"Simply download the beta and let the viscera fly," said Bethesda.
While many players expressed their delight on social media some complained that the new version felt slow and others took to the studio's message boards after facing server problems.
So far, 41% of 1,744 reviews on the Steam platform have been positive.
The BBC has contacted Bethesda for comment.
Doom was first released in 1993 and had 10 million players by 1995.
Software engineer and games developer Gary Riches told the BBC he grew up playing the original Doom games - and completed Doom 2 again just six months ago.
After trying out Doom 4 this morning, he said he felt the pace was much slower than its predecessors due to changes such as a single close-range shot no longer taking out an enemy, and the lack of weapons "hotspots" where weapons were created in the older games.
"I still like Doom 4 but it doesn't feel like Doom 4, it feels like a sequel to Quake or Unreal Tournament," he said.
"To me that's disappointing.
"It's still cool, it looks nice but it has lost what makes it Doom."
However, others were more impressed - YouTuber Matt Unsworth described it on Twitter as "unreal" and SavageCouchSQD said it was "amazing".
The studio behind classic shooter game Doom is inviting players to test the new version for free from 15 to 17 April.