Background. This study was done to analyze the economic effect of clarithromycin on the daily dosing of cyclosporine in lung transplantation. Methods. Nine consecutive patients (mean age ± SEM, 34.6 ± 5.2 years) had transplantation from June 1995 to June 1996. Median follow-up time was 649 days (range, 431 to 799 days). Preoperative diagnoses were cystic fibrosis (n = 4), idiopathic pulmonary fibrosis (n = 2), emphysema, bronchiectasis, and obliterative bronchiolitis. Median time from transplantation to addition of clarithromycin to a standard immunosuppressive regimen was 86 days (range, 14 to 181 days). Results. Baseline cyclosporine dose (9.9 ± 2.2 mg/kg/day) was reduced to 5.8 ± 1.0 mg/kg/day and 4.1 ± 0.8 mg/kg/day at 1 month and 1 year, respectively, after initiation of clarithromycin therapy. Estimated annual savings were $3,400 per patient. There was no increase in infection or rejection episodes. Conclusions. Clarithromycin safely reduced the dose and cost of cyclosporine in this series.