Nadine Kaslow, an association board member and head of a special committee established by the board to oversee the investigation into the organization’s role in interrogations, said she was pleased by the overwhelming vote in favor of the measure. “This is a very resounding ‘yes,’ ” Ms. Kaslow said. The ban was approved by the association’s council by a vote of 156 to 1. Seven council members abstained, while one was recused.

“I think this was a tremendous step in the right direction,” said Susan McDaniel, the association’s president-elect, who was the chairwoman of Friday’s meeting. She expressed hopes that Friday’s vote would persuade psychologists who quit the organization because of its involvement with Bush-era interrogations to rejoin the group.

Many A.P.A. leaders and members said they were stunned by the lopsided vote in favor of the ban, and its backers said that as late as Thursday night they were not certain it would pass. Just before Friday’s vote, the measure’s supporters agreed to change some of the ban’s language, which may have won over some wavering council members. Two of the ban’s advocates on the council, psychologists Scott Churchill and Steven Reisner, insisted that the changes did not weaken the ban. “This was a momentous day,” said Mr. Churchill.

The ban passed on Friday says that “psychologists shall not conduct, supervise, be in the presence of, or otherwise assist any national security interrogations for any military or intelligence entities, including private contractors working on their behalf, nor advise on conditions of confinement insofar as these might facilitate such an interrogation.” The measure’s backers added language on Friday that stated that psychologists may consult with the government on broad interrogation policy, but may not get involved in any specific interrogation or consult on the specific detention conditions for detainees.

The final vote was met by a standing ovation by many of the council members, as well as the large crowd of observers, which included anti-torture activists and psychology graduate students who had come to the meeting to support the ban. Some wore T-shirts proclaiming “First, Do No Harm,” a reference to the physicians’ Hippocratic oath.