In an exhaustive nine-month study on the effects of repealing “don’t ask, don’t tell,” the 17-year-old policy that requires gay service members to keep their sexual orientation secret or face discharge, the authors concluded that while in the short run a repeal would most likely bring about “some limited and isolated disruption to unit cohesion and retention,” it could be mitigated by effective leadership.

The report, by Jeh C. Johnson, the Pentagon’s chief counsel, and Gen. Carter F. Ham, the commander of the United States Army in Europe, also found that much of the concern in the armed forces about openly gay service members was driven by mis-perceptions and stereotypes. Leaving aside those with moral and religious objections to homosexuality, the authors said that the concerns were “exaggerated and not consistent with the reported experiences of many service members.”

At a news conference on Tuesday announcing the release of the report, Defense Secretary Robert M. Gates said that repeal “would not be the wrenching, traumatic change that many have feared and predicted.”

Nonetheless, he said that there were higher levels of “discomfort” about repealing the law among those in the combat branches of the military, and that “those findings remain a source of concern to the service chiefs and to me.” He said the concerns were not insurmountable, but that implementing any repeal should be done carefully and with more preparation of the military’s combat forces.

At the same time, Mr. Gates said it was a “matter of urgency” that the lame-duck Senate vote in the next weeks to repeal the law. If not, he said there would be a fight in the courts and the possibility that the repeal would be “imposed immediately by judicial fiat.”

In a survey of 115,000 service members, the report found distinct differences among the branches of the military. While 30 percent predicted repeal would have some negative effects, some 40 percent to 60 percent of the Marine Corps and those in some combat specialties said it would be negative.

The report also found that a majority — 69 percent — believed they had already worked with a gay man or woman, and of those the vast majority — 92 percent — reported that the unit’s ability to work together was very good, good or “neither good nor poor.”

In the most strongly worded section of the report, the authors concluded that while their mandate was to assess the impact of repealing the “don’t ask, don’t tell” policy — and not whether it should be repealed — they had done just that.

“We are both convinced that our military can do this, even during this time of war,” Mr. Johnson and General Ham wrote. “We do not underestimate the challenges in implementing a change in the law, but neither should we underestimate the ability of our extraordinarily dedicated service men and women to adapt to such change and continue to provide our nation with the military capability to accomplish any mission.”

The study recommended no housing or living changes as a result of a repeal, which must be done by an act of Congress. The authors also quashed any suggestion that there should be separate bathroom facilities.

They called separate bathrooms “a logistical nightmare, expensive and impossible to administer.”