Background: Losartan is a nonpeptide angiotensin II receptor antagonist used in hypertension. The objective of this study was to evaluate the bioequivalence of two losartan formulations, $Sarlotan^{(R)}$ 50 mg tablet (Chong Kun Dang, Pharmaceutical Corp. Seoul, Korea) as a test drug and $Cozaar^{(R)}$ 50 mg tablet (MSD Korea, Co., Ltd., Seoul, Korea) as a reference drug. The bioavailability was evaluated based on the requirement of 20% deviation at a power of 80%. Methods: This study had a randomized, open-label, 2-period, crossover design. There was a 12-hour treatment period for each formulation, with a 1-week washout period between formulations. Each subject received one 50 mg tablet of the reference or test formulation of losartan. Blood samples were obtained during the 12-hour period after the dose in each treatment period. Concentrations of losartan in plasma were analyzed using a liquid chromatography system with tandem mass-spectrometric detection (LC/MS/MS). The primary pharmacokinetic parameters were $C_{max}$ (maximum concentration) and $AUC_t$ (area under the concentration-time curve from time 0 to the last sampling time). Results: A total number of 36 healthy malevolunteers participated in the study and 33 volunteers completed both treatment periods (age range, 19-29 years; mean height, 176.3 cm mean weight, 67.8 kg). The 90% CIs for the geometric mean ratios of the pharmacokinetic parameters (test:reference drug) were 0.96 ~ 1.07 for $AUC_t$ and 0.83 ~ 1.21 for $C_{max}$ lying within the range of the 80% to 125% bioequivalence criterion. Conclusion: The obtained results indicated that pharmacokinetic exposure to $Sarlotan^{(R)}$ tablet was bioequivalent to that of $Cozaar^{(R)}$ tablet.