Reaction of E-rosette formation and agar migration test in vitro showed that small concentrations (7.5.10(-13) -7.5.10(-8) M) of phytosteroid ecdysterone (20-hydroxyecdysone) induce the activation of human lymphocytes. The effect of higher concentrations (7.5.10(-7) -7.5.10(-5) M) is less pronounced