Cilostazol, a type III phosphodiesterase inhibitor, was approved in the United States in 1999 for the reduction of the symptoms of intermittent claudication. This article summarizes the safety data from 8 cilostazol phase 3 controlled clinical trials, involving 2,702 patients: 1,374 receiving cilostazol, 973 assigned to placebo, and 355 taking pentoxifylline. The trials ranged from 12 to 24 weeks in duration. There were a total of 475 patient-exposure years on cilostazol, 357 patient-exposure years on placebo, and 135 patient-exposure years on pentoxifylline. Headache, diarrhea, and other gastrointestinal complaints were seen more often in cilostazol-treated than placebo-treated patients; pharyngitis and nausea were more common in pentoxifylline-treated than placebo-treated patients. Headache requiring discontinuation occurred in 1.3% of patients taking cilostazol 50 mg bid and 3.7% of those receiving cilostazol 100 mg bid, compared with 0.3% of placebo-treated patients. Discontinuations due to diarrhea, palpitations, or myocardial infarction were similar in cilostazol-, placebo-, and pentoxifylline-treated patients. The rate of serious cardiovascular events was similar in all 3 treatment groups. Myocardial infarction occurred in 1.0% of cilostazol-treated, 0.8% of placebo-treated, and 1.1% of pentoxifylline-treated patients. The incidence of stroke was 0.5% in both cilostazol- and placebo-treated patients and 1.1% in pentoxifylline-treated patients. Total cardiovascular morbidity and all-cause mortality was 6.5% for cilostazol 100 mg bid, 6.3% for cilostazol 50 mg bid, and 7.7% for placebo. There were 16 deaths occurring in 0.6%, 0.5%, and 0.6% of cilostazol-, placebo-, and pentoxifylline-treated patients, respectively. The evaluations showed no trend toward increased cardiovascular morbidity or mortality risk in patients receiving cilostazol. In addition, postmarketing surveillance in the United States, representing 70,430 patient-years of cilostazol exposure, has shown minimal accounts of myocardial infarction, stroke, or death. The safety profile of cilostazol in doses of 50 mg bid and 100 mg bid appears to offer an acceptable risk-benefit ratio in patients with intermittent claudication.