Ten patients with advanced urologic cancers who were scheduled to receive at least two courses of chemotherapy were enrolled in this trial. Fifty thousand units of recombinant human interleukin-1 (IL-1) beta analogue OCT-43 (Otsuka Pharmaceutical Co., Ltd., Tokyo, Japan) was administered subcutaneously only once or twice when severe neutropenia (less than 500/microliters) continued for 2 consecutive days. In eight patients, OCT-43 was not injected in the first course of chemotherapy as a control, but was injected in the second course. The durations of leukocytopenia (less than 2000/microliters) and neutropenia (less than 1000/microliters) were significantly shortened in the second course compared with those in the first course in those eight patients. Recovery of neutrophil number from the lowest number was also significantly faster in the second course. Thus, OCT-43 was considered to have hematopoietic activities. However, single or double injection of OCT-43 did not affect the numbers of eosinophilic or basophilic granulocytes, monocytes, or platelets. Adverse effects associated with OCT-43 injections were high fever and chills, but they were controlled by indomethacin.