The investigation was concerned with the leuko-stimulating effect of interleukin-1 beta injected subcutaneously (4.6 +/- 0.3 ng/kg body), daily, for 10 days, to treat toxic leukopenia and neutropenia stage III in cancer patients. Complete recovery of leukocyte levels and granulocytic count (during an average of 9 +/- 1 days) was registered within a period similar to that of intravenous dropwise injection of a single dose of 10-20 ng/kg body. Distinct protective effect on leukopoiesis was achieved following subcutaneous injection of II-1 beta (4.3 +/- 0.2 ng/kg body) in patients with basic leukopenia stage II and neutropenia stage I carried out in conjunction with combination chemotherapy. Due to side effect cytostatic drug administration could be continued.