The authors carried out a study on the blood formation of healthy experimental animals after treatment with the potential antitumours agent taliblastine in view of clarifying its influence. The experiments were undertaken on inbred mice DVA/2 and rats on the Wistar strain. Taliblastine was administered intraperitonealy: in ice-aingly and in a 5-day course, but in rats only in a 5-day course. The substance was administered after single treatment with doses of LD50 maximal threshold limit dose (MTD), but in the dourses with MTD and 1/2 of MTD. They examined the changes in hemoglobin, number of leucocytes, erythrocytes, thrombocytes and reticulocytes, but in rats-the number of bone-marrow cells as well. The values of hematological indices were determined 24 hours, 10 and 30 days after conclusion of the administration of taliblastine. It was established that taliblastine did not affect substantialy the values of hemoglobine and caused transitory changes in the absolute number of leucocytes and lymphocytes.