This study retrospectively evaluated the use of parenteral ciprofloxacin (PC) under the influence of a reserved antimicrobial drug program and an intravenous-oral stepdown program. During the first three months following its formulary introduction, 92 PC treatment courses were initiated. Fifty of these treatment courses in 49 adults were randomly selected for study. The hematology service accounted for 50% of the courses reviewed. The balance were initiated in the intensive care unit (16%), and six other services (34%). PC was used for the treatment of febrile neutropenia (50%), respiratory tract infections (20%), gram-negative sepsis (10%), and five other indications. Initial use of the intravenous formulation was considered appropriate in 92% of courses. Stepdown therapy occurred in 17 (34%) of treatment courses. Of the 26 patients considered candidates for oral therapy, seven patients (27%) were eligible for earlier stepdown and nine patients (35%) did not receive oral drug. According to our criteria, unnecessary use of the intravenous route occurred in 20% of PC treatment days. Mean total cost (acquisition plus delivery) of therapy per course was $668. This cost was higher in the hematology service (mean $990) than any other service (p = 0.0015). When stepdown therapy was employed the mean daily cost of therapy was $43.63 vs. $55.61 when the oral dosage form was not used (p = 0.04). Parenteral drug costs totalling $6245 were avoided by subsequent use of the oral dosage form. If full compliance with stepdown criteria had occurred, an estimated total savings of $10,769 could have been realized.