Background: Udenafil is a new phosphodiesterase (PDE) 5 inhibitor for the treatment of erectile dysfunction. The safety and efficacy of udenafil were shown in clinical studies, and two dosing regimens (100 mg and 200 mg) received marketing approval for 100 mg tablets. In this study, we compared the pharmacokinetics between udenafil 100 mg tablets and 200 mg tablets. Methods: The pharmacokinetic characteristics of the 200 mg strength formulation were compared with the 100 mg strength formulation in an open-labeled, randomized, two-way crossover study in 20 healthy male volunteers. A group of 9 subjects were dosed one udenafil 200 mg tablet and administered two 100 mg tablets one week later. Another group of 11 subjects were dosed in the opposite sequence. As an outcome, plasma udenafil concentration-time profiles were obtained. Pharmacokinetic characteristics were analyzed using the 90% confidence intervals of the geometric mean ratios for maximum plasma concentration ($C_{max}$) and the area under the concentration-time curve from time zero to infinity ($AUC_{inf}$). Results: The two dosage formulations showed similar concentration-time profiles. The geometric mean ratio of $C_{max}$ of udenafil 200 mg formulation to 100 mg formulation was 0.94 and the 90% confidence interval was 0.86-1.02. The geometric mean ratio of $AUC_{inf}$ was 0.93 and the 90% confidence interval for the two regimens was 0.87 - 1.00. Conclusion: The 200 mg tablets showed similar pharmacokinetic characteristics compared to the 100 mg tablets as judged from the 90% confidence intervals of the geometric mean ratio for $C_{max}$ and $AUC_{inf}$ that were both within a range of log 0.80 - log 1.25.