In the 1965 Candidates' matches, he defeated Borislav Ivkov at Bled by 5½–2½ but lost a hard-fought semifinal, also at Bled by 4½–5½ to former World Champion Mikhail Tal, who won the tenth game with a complex speculative knight sacrifice in the center. Larsen won a playoff match for alternates, an eventual third-place Candidates' position, against Efim Geller by 5–4 at Copenhagen 1966 (the first time a Soviet grandmaster had ever been beaten by a non-Soviet in a match). In 1967 he won the Sousse Interzonal with the score of 15½/21 after Fischer withdrew; this placed him 1½ points ahead of the field. He then won his first-round match against Lajos Portisch by 5½–4½ at Porec 1968. In Malmö, however, he lost the semifinal by 2½–5½ to Boris Spassky, who went on to win the title.