The general pharmacological studies of VP 16-213, an antitumor agent, in the peripheral system were carried out by oral and i.v. administration with laboratory animals. VP 16-213 had no effect on the resting tone and spontaneous motility of all the isolated smooth muscle organs tested at concentrations of up to 10(-5) g/ml. VP 16-213 showed no significant influences on the neuromuscular transmission in the sciatic nerve-tibial muscle preparation of rabbits, on renal function in dogs and rats, on blood sugar level in rabbits, and on charcoal meal transport in mice. At a dose of 20 mg/kg, i.v., VP 16-213 reduced gastric secretion in rats. Antiinflammatory, local irritation and hemolytic effects were not observed after the administration of the drug. Single administration of VP 16-213 had orally no effect on the excretion of serum BSP in rats. However, successive administration of the drug (20 mg/kg/day) once daily for 10 days significantly depressed it. VP 16-213 decreased the number of hemolytic plaque forming cells in the spleens of immunized mice.