In the Pew Research Center poll, 49 percent of respondents said it is more important to protect rights of Americans to own guns, compared with 45 percent who say it is more important to control gun ownership.
From 1993 to 2008, Pew said, majorities had said it was more important to control gun ownership than to protect gun rights, and opinion has been divided since early 2009, just before President Barack Obama's election.
The Pew poll also indicated 47 percent of respondents favor allowing gay marriage, compared with 43 percent who said they opposed allowing it.
In 2008, based on an average of polls conducted that year, 39 percent said they favored gay marriage and 51 percent said they opposed it, Pew said.
In 2004, 60 percent said they opposed gay marriage while 31 percent said they supported it.
Results are based on telephone interviews conducted April 4-15 with 3,008 U.S. adults. The poll has sampling error of about 3 percentage points.