WASHINGTON  Attorney General Michael B. Mukasey collapsed during a speech Thursday night and was taken to the hospital after he failed to regain consciousness.

Mr. Mukasey, 67, who took over as attorney general one year ago after the resignation of Alberto R. Gonzales, was giving a speech on national security to members of the Federalist Society, a conservative legal affairs group, when he lost consciousness at about 10:20 p.m.

Around midnight, a Justice Department spokesman said in a statement that Mr. Mukasey was “conscious, conversant and alert.”

The spokesman, Peter A. Carr, said the attorney general would be kept overnight at George Washington University Hospital for observation.