Forty-six noninfected patients undergoing induction chemotherapy for acute nonlymphocytic leukemia were randomized to receive (25 patients) or not to receive (21 control patients) prophylactic granulocyte transfusions when their granulocyte count fell below 0.5 X 10(9)/L. Septicemia was less frequent in the patients who received transfusions (two in 25 patients) than in the control patients (five in 21 patients), but this difference was not statistically significant (p = 0.28). Moreover, pneumonia was more frequent among the transfused patients (12 in 25 patients versus two in 21 patients, p = 0.01). There were no significant differences between the two groups in the frequency of other documented infections, the achievement or duration of remission, or survival. Recipients of prophylactic granulocyte transfusions had a higher prevalence of cytomegalovirus infections (13 in 21 patients versus five in 19 patients, p = 0.03). These results suggest that prophylactic granulocyte transfusions have no statistically significant effect on the frequency of septicemia or other infections, do not enhance remission rates or survival, and are associated with an increased risk for pulmonary complications and cytomegalovirus infections.