We compared clinical outcomes of 65 hospitalized patients receiving clindamycin before and 59 after a sudden hospitalwide shift in dosing schedules for this drug from 600 mg every 6 hours to 600 mg every 8 hours. Outcomes studied included the efficacy of antibiotic treatment, length of febrile period, and frequency of adverse effects. We also compared and controlled for patient characteristics such as age, sex, presence of multiple diagnoses, length of therapy, and concurrent use of other antibiotics. There were no differences in measured clinical outcomes between the two groups. Treatment was successful in 87% of both groups. The average number of febrile days was 5.1 in the first group and 3.9 in the second (P less than .05). Patients on 6-hourly therapy experienced a 12% rate of antibiotic-related adverse effects vs. 5% for the 8-hourly group (P greater than .05). These data support the clinical rationale and safety of a hospitalwide reduction in the frequency of clindamycin dosing. In addition to considerable pharmacy and nursing time saved, this change also saved greater than $40,000 annually in antibiotic costs.