NEW YORK - Pittsburgh Steelers quarterback Ben Roethlisberger was suspended for six games without pay Wednesday for violating the NFL's personal conduct policy and ordered to undergo behavioral evaluation.

Commissioner Roger Goodell handed down the punishment a week after prosecutors decided not to charge Roethlisberger in a case involving a 20-year-old college student who accused him of sexually assaulting her in a Georgia nightclub in March.

Goodell said the league's conduct policy gave him the right to impose discipline regardless of whether he broke the law.

"I recognize that the allegations in Georgia were disputed and that they did not result in criminal charges being filed against you," he said in his letter to the two-time Super Bowl winner, a six-year veteran.

"My decision today is not based on a finding that you violated Georgia law, or on a conclusion that differs from that of the local prosecutor. That said, you are held to a higher standard as an NFL player, and there is nothing about your conduct in Milledgeville that can remotely be described as admirable, responsible, or consistent with either the values of the league or the expectations of our fans."

Roethlisberger must undergo a "comprehensive behavioral evaluation by medical professionals" and may not attend any team offseason activities until that evaluation is completed.

The suspension could be reduced to four games for good behavior. Sitting out all six games would cost him an estimated $2.8 million.

Before acting, Goodell said he interviewed Roethlisberger on April 13 and talked to current and former players and the players' union. He also reviewed information from the Georgia Bureau of Investigation and Milledgeville police and talked privately with Georgia district attorney Fred Bright. In addition, Goodell said he listened to recommendations from the quarterback's representatives and took into account information learned by the NFL office regarding the alleged assault.

"Your conduct raises sufficient concerns that I believe effective intervention now is the best step for your personal and professional welfare," Goodell said in the letter. "In your six years in the NFL, you have first thrilled and now disappointed a great many people. I urge you to take full advantage of this opportunity to get your life and career back on track."

Roethlisberger also is being sued by a woman who accused him of raping her at a Lake Tahoe hotel-casino in 2008. He denied the allegation and wasn't charged.

Goodell has aggressively dealt with players who violated the personal conduct policy throughout his 3½ years as commissioner. He banned Adam "Pacman" Jones for one year, and suspended Tank Johnson and Chris Henry eight games each in 2007.

Last year, Michael Vick was suspended for six games, later shortened to two games, for his role in a dogfighting ring. Vick also spent 18 months in jail.