user8620: There are quite a few grandmaster games with 3 queens or 4 queens, but what is the highest number of queens on the board in a game between two GMs?  
I'd be interested in both the most on the board at the same time and the most total during the game. 

user4324: If you have a PGN file of chess games you can use CQL to search it. Something like:
(match
  :pgn src.pgn
  :output queens.pgn
  (position
    :piececount [Qq] 3 8))

Should return all games with positions containing 3 to 8 Queens on the board.
Edit: The Aquarium interface from chessok has a CQL search capability and can read ChessBase databases, so I was able to search my reference database (5M+ games) to games with 5 or more queens. There were no GM games with more than 5 queens on the board. The Anton Guijarro - Franco game mentioned by dfan, is a GM (Anton) vs an IM (Franco). In addition to the Miton - Benjamin game mentioned by dfan, I found a game played about a month later, Hickl - Sokolov that had 5 queens.
Miton - Benjamin:
[Event "World op 33rd Philadelphia  6/??/2005"]
[Site "?"]
[Date "2005.07.03"]
[Round "7"]
[White "Miton Kamil"]
[Black "Benjamin Joel"]
[Result "1-0"]
[Annotator ""]
[BlackElo "2563"]
[ECO "E33"]
[GameNo "3367517"]
[Source "ChessBase 11/10/1998"]
[WhiteElo "2592"]
[FEN ""]

1. d4 Nf6 2. Nf3 Nc6 3. c4 e6 4. Nc3 Bb4 5. Qd3 d6 6. a3 Bxc3+ 7. Qxc3 O-O 8.
e3 a5 9. Be2 Re8 10. b3 e5 11. d5 Ne7 12. Nd2 Bf5 13. O-O c6 14. dxc6 Nxc6 15.
Rd1 Rc8 16. Qb2 Qe7 17. Nb1 b5 18. Nc3 bxc4 19. bxc4 Ne4 20. Nb5 Red8 21. f3
Nc5 22. e4 Be6 23. Be3 Rb8 24. Qc3 a4 25. Rac1 Nb3 26. Rc2 h6 27. f4 f6 28.
Qe1 Bf7 29. Qf2 exf4 30. Qxf4 Ne5 31. Nc3 Nc5 32. Nd5 Bxd5 33. cxd5 Rb3 34.
Bxc5 dxc5 35. Bc4 Nxc4 36. Rxc4 Rxa3 37. d6 Qe6 38. Rxc5 Rb3 39. Ra5 a3 40.
Ra7 Rd7 41. Rxd7 Qxd7 42. e5 Rb2 43. Qc4+ Kh7 44. e6 Qa7+ 45. Qd4 Qb7 46. Qd3+
g6 47. Qf1 a2 48. e7 Rb1 49. e8=Q a1=Q 50. d7 Qb6+ 51. Kh1 Rxd1 52. Qe7+ Kg8
53. d8=Q+ Qxd8 54. Qxd8+ Rxd8 55. Qxa1 Rc8 56. h4 Rd8 57. Qa2+ Kg7 58. Kg1 Rd7
59. Kf2 Re7 60. Kf3 Rf7 61. Qa8 Re7 62. Qd8 Re5 63. Qd7+ Kf8 64. Qh7 Re6 65.
Qh8+ Kf7 66. Qc8 Ke7 67. Qh8 g5 68. Qh7+ Kd6 69. Qg7 Ke5 70. Qxh6 Rd6 71. Qh7
Re6 72. Qh5 1-0

Hickl - Sokolov:
[Event "Mainz Ordix op Mainz  8/13/2005"]
[Site "?"]
[Date "2005.08.14"]
[Round "7"]
[White "Hickl Joerg"]
[Black "Sokolov Ivan"]
[Result "1-0"]
[Annotator ""]
[BlackElo "2691"]
[ECO "A07"]
[GameNo "3404712"]
[Source "ChessBase 11/10/1998"]
[WhiteElo "2537"]
[FEN ""]

1. g3 d5 2. Nf3 c6 3. Bg2 Bg4 4. b3 Nd7 5. Bb2 Bxf3 6. Bxf3 e5 7. d3 Ngf6 8.
O-O h5 9. c4 d4 10. Re1 Bc5 11. Na3 Bb4 12. Rf1 Nf8 13. Nc2 Be7 14. e3 Ne6 15.
exd4 exd4 16. Re1 Qd7 17. Qd2 h4 18. Rad1 Rd8 19. b4 Kf8 20. Re2 c5 21. bxc5
Bxc5 22. Nb4 hxg3 23. hxg3 Nc7 24. Rde1 a5 25. Nc2 b6 26. Ba3 Ne6 27. Re5 g6
28. Rxe6 fxe6 29. Bxc5+ bxc5 30. Qxa5 Rc8 31. Na3 Kg7 32. Re5 Qe7 33. Nb5 Nd7
34. Re2 Qg5 35. Qe1 e5 36. Nd6 Rb8 37. Bg2 Rb6 38. Nb5 Ra6 39. Rb2 Rb8 40. Bh3
Nf6 41. Re2 e4 42. dxe4 Nh5 43. Bg2 Rab6 44. e5 d3 45. Rd2 Rxb5 46. cxb5 c4
47. e6 Rd8 48. Rd1 d2 49. Qe4 c3 50. b6 Qf5 51. e7 c2 52. Rf1 d1=Q 53. exd8=Q
Qxd8 54. Qb4 Qd1 55. b7 c1=Q 56. b8=Q Qxf1+ 57. Bxf1 Nf6 58. Q4f8+ 1-0

Anton Guijarro - Franco:
[Event "XXI Elgoibar Magistral Elgoibar ESP 12/14/2011"]
[Site "?"]
[Date "2011.12.18"]
[Round "6.4"]
[White "Anton Guijarro D"]
[Black "Franco Alonso A"]
[Result "1-0"]
[Annotator ""]
[BlackElo "2454"]
[ECO "A17"]
[GameNo "4719077"]
[Source "ChessBase 11/10/1998"]
[WhiteElo "2469"]
[FEN ""]

1. Nf3 Nf6 2. c4 e6 3. Nc3 b6 4. g3 Bb7 5. Bg2 Be7 6. O-O O-O 7. Re1 Ne4 8.
Nxe4 Bxe4 9. d3 Bb7 10. e4 c5 11. d4 cxd4 12. Nxd4 Nc6 13. Bf4 Nxd4 14. Qxd4
Bc5 15. Qd2 Qe7 16. a3 e5 17. Be3 a5 18. Rad1 Bc6 19. Bh3 Ra7 20. Bg5 f6 21.
Be3 a4 22. Bf1 Qe6 23. Qd3 Rc8 24. h4 Rac7 25. Kh2 Qe7 26. Rd2 Bxe3 27. Qxe3
Qc5 28. Qf3 Rf8 29. Qg4 Rcc8 30. h5 Rce8 31. Re3 Re6 32. Qd1 Re7 33. Bh3 Rff7
34. Bf5 Qxc4 35. Rc3 Qb5 36. Kg2 Rf8 37. Qg4 Kh8 38. Rcd3 Qc4 39. Rd6 Bb5 40.
Bxd7 Qf1+ 41. Kh2 Bxd7 42. Rxd7 Rxd7 43. Qxd7 h6 44. Qe7 Rg8 45. Qd6 Qe1 46.
Qb4 b5 47. Kg2 Kh7 48. Rd5 Qe2 49. Rd7 Rc8 50. Rxg7+ Kxg7 51. Qe7+ Kg8 52.
Qe6+ Kg7 53. Qd7+ Kf8 54. Qxc8+ Ke7 55. Qf5 Qxb2 56. Qh7+ Ke6 57. Qxh6 b4 58.
Qg6 bxa3 59. h6 a2 60. h7 a1=Q 61. Qf5+ Kd6 62. h8=Q Kc5 63. Qf8+ Kc4 64. Qe6+
Kd3 65. Qfxf6 Qd4 66. Qf3+ Kd2 67. Qh6+ Kc2 68. Qc6+ Kb1 69. g4 Qab2 70. g5 a3
71. g6 a2 72. g7 a1=Q 73. g8=Q Qaa3 74. Qgg3 Qxf3+ 75. Qxf3 Qc2 76. Qb5+ Qcb2
77. Qfd3+ Qxd3 78. Qxd3+ Kc1 79. Kf3 Qd4 80. Qe2 Qd6 81. Qc4+ Kd2 82. Qd5+ 1-0


user291: This sounds like a job for Tim Krabbé, who presents two games with six queens: Szalanczy - Nguyen, Budapest 2009 and Anton - Franco, XXI Elgoibar Magistral 2011. I don't know how many of the participants were grandmasters.
There are some other games with 5+ queens at Chess Siberia. Of these, Miton - Benjamin, World Open Philadelphia 2005 definitely features two grandmasters.

8620: <p>There are quite a few grandmaster games with 3 queens or 4 queens, but what is the highest number of queens on the board in a game between two GMs?  </p>

<p>I'd be interested in both the most on the board at the same time and the most total during the game. </p>
 4324: <p>If you have a PGN file of chess games you can use <a href="https://web.archive.org/web/20140130143815/http://www.rbnn.com/cql/" rel="nofollow noreferrer">CQL</a> to search it. Something like:</p>
<pre><code>(match
  :pgn src.pgn
  :output queens.pgn
  (position
    :piececount [Qq] 3 8))
</code></pre>
<p>Should return all games with positions containing 3 to 8 Queens on the board.</p>
<p><strong>Edit:</strong> The Aquarium interface from chessok has a CQL search capability and can read ChessBase databases, so I was able to search my reference database (5M+ games) to games with 5 or more queens. There were no GM games with more than 5 queens on the board. The Anton Guijarro - Franco game mentioned by dfan, is a GM (Anton) vs an IM (Franco). In addition to the Miton - Benjamin game mentioned by dfan, I found a game played about a month later, Hickl - Sokolov that had 5 queens.</p>
<p>Miton - Benjamin:</p>
<pre><code>[Event &quot;World op 33rd Philadelphia  6/??/2005&quot;]
[Site &quot;?&quot;]
[Date &quot;2005.07.03&quot;]
[Round &quot;7&quot;]
[White &quot;Miton Kamil&quot;]
[Black &quot;Benjamin Joel&quot;]
[Result &quot;1-0&quot;]
[Annotator &quot;&quot;]
[BlackElo &quot;2563&quot;]
[ECO &quot;E33&quot;]
[GameNo &quot;3367517&quot;]
[Source &quot;ChessBase 11/10/1998&quot;]
[WhiteElo &quot;2592&quot;]
[FEN &quot;&quot;]

1. d4 Nf6 2. Nf3 Nc6 3. c4 e6 4. Nc3 Bb4 5. Qd3 d6 6. a3 Bxc3+ 7. Qxc3 O-O 8.
e3 a5 9. Be2 Re8 10. b3 e5 11. d5 Ne7 12. Nd2 Bf5 13. O-O c6 14. dxc6 Nxc6 15.
Rd1 Rc8 16. Qb2 Qe7 17. Nb1 b5 18. Nc3 bxc4 19. bxc4 Ne4 20. Nb5 Red8 21. f3
Nc5 22. e4 Be6 23. Be3 Rb8 24. Qc3 a4 25. Rac1 Nb3 26. Rc2 h6 27. f4 f6 28.
Qe1 Bf7 29. Qf2 exf4 30. Qxf4 Ne5 31. Nc3 Nc5 32. Nd5 Bxd5 33. cxd5 Rb3 34.
Bxc5 dxc5 35. Bc4 Nxc4 36. Rxc4 Rxa3 37. d6 Qe6 38. Rxc5 Rb3 39. Ra5 a3 40.
Ra7 Rd7 41. Rxd7 Qxd7 42. e5 Rb2 43. Qc4+ Kh7 44. e6 Qa7+ 45. Qd4 Qb7 46. Qd3+
g6 47. Qf1 a2 48. e7 Rb1 49. e8=Q a1=Q 50. d7 Qb6+ 51. Kh1 Rxd1 52. Qe7+ Kg8
53. d8=Q+ Qxd8 54. Qxd8+ Rxd8 55. Qxa1 Rc8 56. h4 Rd8 57. Qa2+ Kg7 58. Kg1 Rd7
59. Kf2 Re7 60. Kf3 Rf7 61. Qa8 Re7 62. Qd8 Re5 63. Qd7+ Kf8 64. Qh7 Re6 65.
Qh8+ Kf7 66. Qc8 Ke7 67. Qh8 g5 68. Qh7+ Kd6 69. Qg7 Ke5 70. Qxh6 Rd6 71. Qh7
Re6 72. Qh5 1-0
</code></pre>
<p>Hickl - Sokolov:</p>
<pre><code>[Event &quot;Mainz Ordix op Mainz  8/13/2005&quot;]
[Site &quot;?&quot;]
[Date &quot;2005.08.14&quot;]
[Round &quot;7&quot;]
[White &quot;Hickl Joerg&quot;]
[Black &quot;Sokolov Ivan&quot;]
[Result &quot;1-0&quot;]
[Annotator &quot;&quot;]
[BlackElo &quot;2691&quot;]
[ECO &quot;A07&quot;]
[GameNo &quot;3404712&quot;]
[Source &quot;ChessBase 11/10/1998&quot;]
[WhiteElo &quot;2537&quot;]
[FEN &quot;&quot;]

1. g3 d5 2. Nf3 c6 3. Bg2 Bg4 4. b3 Nd7 5. Bb2 Bxf3 6. Bxf3 e5 7. d3 Ngf6 8.
O-O h5 9. c4 d4 10. Re1 Bc5 11. Na3 Bb4 12. Rf1 Nf8 13. Nc2 Be7 14. e3 Ne6 15.
exd4 exd4 16. Re1 Qd7 17. Qd2 h4 18. Rad1 Rd8 19. b4 Kf8 20. Re2 c5 21. bxc5
Bxc5 22. Nb4 hxg3 23. hxg3 Nc7 24. Rde1 a5 25. Nc2 b6 26. Ba3 Ne6 27. Re5 g6
28. Rxe6 fxe6 29. Bxc5+ bxc5 30. Qxa5 Rc8 31. Na3 Kg7 32. Re5 Qe7 33. Nb5 Nd7
34. Re2 Qg5 35. Qe1 e5 36. Nd6 Rb8 37. Bg2 Rb6 38. Nb5 Ra6 39. Rb2 Rb8 40. Bh3
Nf6 41. Re2 e4 42. dxe4 Nh5 43. Bg2 Rab6 44. e5 d3 45. Rd2 Rxb5 46. cxb5 c4
47. e6 Rd8 48. Rd1 d2 49. Qe4 c3 50. b6 Qf5 51. e7 c2 52. Rf1 d1=Q 53. exd8=Q
Qxd8 54. Qb4 Qd1 55. b7 c1=Q 56. b8=Q Qxf1+ 57. Bxf1 Nf6 58. Q4f8+ 1-0
</code></pre>
<p>Anton Guijarro - Franco:</p>
<pre><code>[Event &quot;XXI Elgoibar Magistral Elgoibar ESP 12/14/2011&quot;]
[Site &quot;?&quot;]
[Date &quot;2011.12.18&quot;]
[Round &quot;6.4&quot;]
[White &quot;Anton Guijarro D&quot;]
[Black &quot;Franco Alonso A&quot;]
[Result &quot;1-0&quot;]
[Annotator &quot;&quot;]
[BlackElo &quot;2454&quot;]
[ECO &quot;A17&quot;]
[GameNo &quot;4719077&quot;]
[Source &quot;ChessBase 11/10/1998&quot;]
[WhiteElo &quot;2469&quot;]
[FEN &quot;&quot;]

1. Nf3 Nf6 2. c4 e6 3. Nc3 b6 4. g3 Bb7 5. Bg2 Be7 6. O-O O-O 7. Re1 Ne4 8.
Nxe4 Bxe4 9. d3 Bb7 10. e4 c5 11. d4 cxd4 12. Nxd4 Nc6 13. Bf4 Nxd4 14. Qxd4
Bc5 15. Qd2 Qe7 16. a3 e5 17. Be3 a5 18. Rad1 Bc6 19. Bh3 Ra7 20. Bg5 f6 21.
Be3 a4 22. Bf1 Qe6 23. Qd3 Rc8 24. h4 Rac7 25. Kh2 Qe7 26. Rd2 Bxe3 27. Qxe3
Qc5 28. Qf3 Rf8 29. Qg4 Rcc8 30. h5 Rce8 31. Re3 Re6 32. Qd1 Re7 33. Bh3 Rff7
34. Bf5 Qxc4 35. Rc3 Qb5 36. Kg2 Rf8 37. Qg4 Kh8 38. Rcd3 Qc4 39. Rd6 Bb5 40.
Bxd7 Qf1+ 41. Kh2 Bxd7 42. Rxd7 Rxd7 43. Qxd7 h6 44. Qe7 Rg8 45. Qd6 Qe1 46.
Qb4 b5 47. Kg2 Kh7 48. Rd5 Qe2 49. Rd7 Rc8 50. Rxg7+ Kxg7 51. Qe7+ Kg8 52.
Qe6+ Kg7 53. Qd7+ Kf8 54. Qxc8+ Ke7 55. Qf5 Qxb2 56. Qh7+ Ke6 57. Qxh6 b4 58.
Qg6 bxa3 59. h6 a2 60. h7 a1=Q 61. Qf5+ Kd6 62. h8=Q Kc5 63. Qf8+ Kc4 64. Qe6+
Kd3 65. Qfxf6 Qd4 66. Qf3+ Kd2 67. Qh6+ Kc2 68. Qc6+ Kb1 69. g4 Qab2 70. g5 a3
71. g6 a2 72. g7 a1=Q 73. g8=Q Qaa3 74. Qgg3 Qxf3+ 75. Qxf3 Qc2 76. Qb5+ Qcb2
77. Qfd3+ Qxd3 78. Qxd3+ Kc1 79. Kf3 Qd4 80. Qe2 Qd6 81. Qc4+ Kd2 82. Qd5+ 1-0
</code></pre>
 291: <p>This sounds like a job for <a href="http://timkr.home.xs4all.nl/records/records.htm#Most%20queens">Tim Krabbé</a>, who presents two games with six queens: Szalanczy - Nguyen, Budapest 2009 and Anton - Franco, XXI Elgoibar Magistral 2011. I don't know how many of the participants were grandmasters.</p>

<p>There are some other games with 5+ queens at <a href="http://www.chessib.com/five-six-queens-chess-games.html">Chess Siberia</a>. Of these, <a href="http://www.chessgames.com/perl/chessgame?gid=1667656">Miton - Benjamin</a>, World Open Philadelphia 2005 definitely features two grandmasters.</p>
