This study examined the effects of rotation stress (78 circles per 1 min for 1 h: 10 min rotation + 5 min interval) on peritoneal macrophage release of lymphocyte-activating factors (LAF) and interleukin-1 alpha (IL-1 alpha) concentration in mice (CBA x C57BL6)F1. Rotation stress induced the macrophages' release of LAF with peak reactions in 0-1 h after termination of stress, followed by elevation of plasma IL-1 alpha. Induction of LAF release was accompanied by a higher concentration of corticosterone (Cs) in the blood, most prominent at 0 and 0.5 h after termination of the stressful procedure, and recovering to normal values 1 h later. It is suggested that the stimulating effect of stress on LAF and IL-1 production possibly involves glucocorticoid hormones, as well as other stress-induced neurohumoral shifts accompanying the reaction of glucocorticoids. It is also possible that the activated production of LAF and IL-1 by macrophages has a stress-limiting role in cases of mild stress.