A drug utilization evaluation (DUE) of cimetidine surveyed use, dose, route of administration, indications, and safety in five New York hospitals. Drug use and patient information were recorded on cimetidine data collection forms; data on indications were noted on physician response forms. In addition to FDA-approved indications, cimetidine was frequently used for non-approved indications substantiated by the H2-antagonist literature. Prophylaxis accounted for 42.5% of total use, followed by nonulcer (25.5%), ulcer (18.8%), and other indications (13.1%). Appropriateness of dosage could not be determined in 42 (16.1%) patients with insufficient creatinine clearance data. One hundred and thirty patients (49.8%) whose renal function could be estimated were within dosage guidelines; 89 (34.1%) were above or below dosage recommendations. The incidence of adverse effects was low (3.83%), although many patients were "at risk" of untoward events or drug-drug interactions.