Guidelines, implemented by clinical pharmacists, were developed by the pharmacy and therapeutics subcommittee on a dedicated service caring for hospitalized patients with human immunodeficiency virus infection or the acquired immunodeficiency syndrome (AIDS) who required granulocyte colony-stimulating factor (G-CSF) therapy. Drug use and evaluation was conducted on all patients with AIDS who were prescribed G-CSF, and education was provided to medical house staff. Clinical data from chart review and laboratory and billing data bases of the hospital medical information system were compared for the 9-month intervention period (IP) with data from the 9-month preintervention period (PIP). Comparing the IP and PIP, the mean number of G-CSF doses (0.29 vs 0.51) and pharmacy costs per day ($112 vs $200) decreased, with no change in the number of patients requiring G-CSF. The 1.3 pharmacist interventions per patient resulted in a decrease to 2.4 doses per admission from a baseline of 5.9 (p<0.0001). Mean hospital stay (11.9 vs 13.8 days) and mean number of days of neutropenia did not differ for IP and PIP groups. Effectively implemented pharmacist-based interventions can decrease hospital costs without increasing patient morbidity.