In 28 patients with hematologic malignancy, the clinical effect and the safety of sulbactam/cefoperazone (SBT/CPZ) were studied on 45 episodes during granulocytopenic stage after antineoplastic chemotherapy. The overall efficacy rate obtained with SBT/CPZ in combination with other drugs was 62%. The rates for sepsis, suspected sepsis and pneumonia were 67%, 94% and 38%, respectively. The efficacy in those cases that showed granulocyte count less than 300/microliters during the course of administration of SBT/CPZ was 53%, and in those cases that showed granulocyte counts recovery to more than 300/microliters was 73%. Prior antimicrobiological treatments had no influence on the efficacy of SBT/CPZ. SBT/CPZ showed an activity spectrum covering frequently isolated microorganism including Acinetobacter calcoaceticus, Pseudomonas aeruginosa, Enterobacter cloacae and Staphylococcus aureus. Mild adverse effect were observed in 4 episodes (8.8%). These result suggested that SBT/CPZ was thought to be a useful drug for empirical therapy in granulocytopenic patients with hematologic malignancies.