'Social buffering'--the apparent capacity of group membership to reduce the adrenocortical response to stress, was investigated in squirrel monkeys by means of a between-within experimental design. Adult males were assigned to two groups. Group paired (n = 6) received pairings of a conditional stimulus (CS) with footshock. Group control (n = 6) received CS presentations without shock. All animals were then tested with 10 presentations of the CS without shock under three social-housing conditions, in four successive phases of the experiment: individual, dyad, group, and individual housing. Neither group showed a cortisol response to the CS prior to training. Following training, CS-evoked elevations of cortisol were found only in group paired, and only in the individual housing conditions. These results replicate and extend our previous finding that the presence of conspecifics can ameliorate a neuroendocrine response to psychological stressors in squirrel monkeys.