Cilostazol controlled-release (CR) tablets have recently been developed by Korea United Pharm (Seoul, Korea). The tablets use a patented double CR system, which improves drug compliance by allowing "once daily" administration and reduces adverse events by sustaining a more even plasma concentration for 24 h. We conducted an open, randomized, two-period, two-treatment, crossover study to compare the pharmacokinetic (PK) characteristics and tolerability of cilostazol when administered to healthy Korean male volunteers as CR or immediate release (IR) tablets (Pletal, Korea Otsuka Pharmaceutical Co., Gyeonggi-do, Korea). Each volunteer was randomly allocated to receive a single tablet of cilostazol CR (200 mg) or two tablets of cilostazol IR (100 mg) with a 7-day washout period between treatments. Plasma cilostazol, OPC-13015 (3,4-dehydrocilostazol), and OPC-13213 (4'-trans-hydroxycilostazol) were assayed using liquid chromatography-tandem mass spectrometry for PK analysis. Thirty participants completed the study with no clinically relevant safety issues. The peak concentrations (C max , mean ± SD) of cilostazol CR and cilostazol IR were 1414.6 ± 49.3 and 1413.1 ± 35.2 ng/mL, respectively, and the areas under the plasma concentrationtime curve from 0 to the last concentration (AUC last ) were 23928.7 ± 65.9 and 25312.0 ± 62.6 ng•h/ mL, respectively. The geometric mean ratios (cilostazol CR/ cilostazol IR, GMR) of the C max and AUC last values were 1.001 (90% CI: 0.822, 1.220) and 0.945 (90% CI: 0.814, 1.098), respectively. The frequencies of adverse events were similar. The present study showed that cilostazol PK and tolerability were comparable when administered to healthy Korean men, regardless of whether administered as cilostazol CR or IR.