The Washington newspaper's survey found 18 senators have never made the trip, with one of them, Sen. Jim Webb, D-Va., calling the junkets political "dog and pony shows."
The leader of the traveling pack is Sen. Jack Reed, D-R.I., who has visited Iraq 10 times, including three trips in the past year. Sen. James Inhofe, R-Okla., an ardent supporter of the war effort, has made eight trips to Iraq.
Eight other senators have made at least six trips since the war began in March 2003.
James Thurber, professor of political science and director of the Center for Congressional and Presidential Studies at American University, told the newspaper the visits make sense politically.
"The more trips you go give you more authority," Thurber said.