A Marine Corps survey found about 17 percent of male Marine respondents said they would likely leave the Corps if women move into combat positions.
That number jumped to 22 percent if women are assigned involuntarily to those jobs, according to the survey.
Results of the survey of 53,000 Marines were released to The Associated Press on Friday.
The survey was conducted last summer and the results were given to Defense Secretary Leon Panetta before he opened thousands of combat jobs to female service members last week.
About 4 percent of female Marines surveyed said they would consider leaving if the ban was lifted. Even more would drop out if women were put into those positions involuntarily with about 17 percent of female respondents expressing they would cut their careers short under those circumstances.
About 31 percent of female respondents say they would be interested in moving into a combat position.
The commandant of the Marine Corps said the infantry side of the most male of all military branches is skeptical about how women will perform in their units, and some positions may end up closed again if too few females meet the physically demanding standards of combat.
Gen. James Amos made the remarks to reporters Thursday at a defense conference in San Diego hosted by the U.S. Naval Institute and the defense trade group AFCEA.
Amos says most Marines support the policy change. He pointed out that over the past decade, many male service members already have been fighting alongside women in Iraq and Afghanistan.
Women who serve in supply troops, as clerks and with military police have ended up on the unmarked front lines of modern warfare, blurring the distinction between combat and noncombat jobs. More than 150 women have been killed in wars in Iraq and Afghanistan while serving in support roles.
Many of the newly opened positions are in Army and Marine infantry units and in potentially elite commando jobs. It will be up to the military service chiefs to recommend and defend whether women should be excluded from any of those more demanding and deadly positions, such as Navy commandos or the Army's Delta Force.
The infantry units are smaller and spend more grueling time in battle.
"I think from the infantry side of the house, you know they're more skeptical," Amos said. "It's been an all-male organization throughout the history of the U.S. Marine Corps so I don't think that should be any surprise."
The Marine Corps is the most male of all the military branches. About 7 percent of Marines are female compared to about 14 percent overall for the armed forces.