Ion implantation of Be into GaAs, followed by annealing at temperatures above 475°C, produces layers with strong p-type conductivity and high hole mobility. Maximum electrical activation of the Be is obtained by 550°C. Be appears to be the only dopant in GaAs which can be electrically activated at such low temperatures following implantation. At temperatures in the range 500-630°C, satisfactory electrical results can be obtained by annealing in argon or vacuum without encapsulation. Little change in the electrical properties occurs for subsequent encapsulated annealing at temperatures up to 800°C for the fluences used.