After years of debate and months of final preparations, the military can no longer prevent gays from serving openly in its ranks.
Repeal of a 1993 law that allowed gays to serve only so long as they kept their sexual orientation private took effect Tuesday at 12:01 a.m. ET.
Some in Congress remain opposed to the change, arguing that it may undermine the military's ability to recruit or fight wars. But top Pentagon leaders said that won't happen.
As of last week, 97 percent of the military had undergone training in the new law.
The military was already accepting applications from openly gay recruits, but they had to wait for the repeal to take effect before processing the applications.
With the lifting of the ban, the Defense Department will publish revised regulations to reflect the new law allowing gays to serve openly.
The revisions, such as eliminating references to banned homosexual service, are in line with policy guidance that was issued by top Pentagon officials in January, after Obama signed the legislation that did away with the "don't ask, don't tell" policy.
The policy was established 18 years ago by the Clinton administration.
Though "don't ask, don't tell" is now history, there are still hurdles for gays in the military.
Surveys have shown that most military officers and enlisted are prepared for the change. There have been critics who have been concerned about unit cohesion with gays serving openly, especially in times of combat.
But other studies have shown that shouldn't be a problem.
Former Marine Cpl. Marvil Greene was in charge of most of the Marine Corps graduating ceremonies in San Diego until someone threatened to out him.
In 1997, Greene had to leave the Marine Corps because of "don't ask, don't tell." Green says the military will never be the same with the repeal.
The Associated Press contributed to this report.