The effect of morphine (10(-6) M) and adrenaline (0.2 microgram/10(6) cells) on the oxidant and antioxidant activity in cells of the immunophagocytic system was compared in vitro. Morphine and adrenaline caused different changes in production of active forms of oxygen (AFA) and antioxidant activity of the enzymes superoxide dismutase and glutathione reductase in neutrophils, monocytes, and lymphocytes in human peripheral blood. The effect of these drugs, however, was unidirectional in character in each type of cells. Eleutherococcus (obtained in the drug-store and diluted 10- to 11-fold) or indomethacin (10(-7) M) injected together with morphine removed the morphine-induced increase of APA production in the neutrophils, they also prevented the effect of morphine on enzyme activation in the neutrophils and monocytes, but had no influence on the effect of morphine on the antioxidant enzymes in the neutrophils. The results of the study point to the existence of common mediators in direct action of adrenaline and morphine on the cells of the immunophagocytic system.