The diffusion brazing of butt joints in 6061 and 7075 aluminum alloys in a vacuum atmosphere with mechanical pressure perpendicular to the joint was investigated. Filler metals included silver, gold, copper, magnesium, zinc, Al12Si and Ag28Cu in the form of foil, powder, electroplated deposits, and vapor deposits. Joints were examined by metallography, bend tests, tensile tests, and other mechanical tests. No successful filler metal for 7075 aluminum was developed. Both silver and Al12Si filler metal in foil form produced joints in 6061 aluminum with the tensile strength of the base metal in the T6 condition. The tensile elongation and bend ductility was good in both as-brazed and T6 conditions.