Thalidomide, a derivative of alpha-N-phthalimidoglutarimide acid, was withdrawn from the market in the 1960s because of severe birth defects. Recent reports have suggested antiangiogenic and antitumor activity of this drug. We have treated 52 patients with refractory multiple myeloma at age from 32 to 79 years (mean 63) with thalidomide at a dose of 200-400 mg daily. Out of the group of 52 patients, 27 patients (52%) responded to the therapy, in 25 patients (48%) a response was not achieved (decline in monoclonal protein was smaller than 25%). There was a systematic improvement in haemoglobin concentration, erythrocyte count and thrombocyte count during thalidomide therapy. Leukocyte count showed an inclination to decrease, however observed changes were not statistically significant. The improvement in morphotic parameters of blood was observed both in responder and nonresponder patients.