OBJECTIVE A randomized, two-way, crossover bioequivalence study in 24 healthy Korean male volunteers was conducted to compare bioequivalence of two brands of 20 mg omeprazole capsules, Hutex omeprazole (Hutex Pharm Co. Korea) as a test and Yuhan Losec (Yuhan Co. Ltd., Korea) as a reference drug. METHODS Subjects were administered single dosage of 1 capsule of 20 mg of each formulation with 240 ml of water after 10 hs overnight fasting on 2 treatment days separated by one-week washout period. After dosing, serial blood sampling was held during 9 hs. Plasma was analyzed for omeprazole by a validated HPLC method with ultraviolet detection in the range of 10 approximately 1,000 ng/ml with the lowest limit of quantification of 10 ng/ml. RESULTS Several pharmacokinetic (PK) parameters were determined from the plasma samples, and data from reference and test formulations in the plasma were represented such as AUC0-t (1,223.3 vs 1,284.3 ng x h/ml), [formula in text](1,311.1 vs 1,410.0 ng x h/ml), Cmax (598.7 vs 598.1 ng/ml), tmax (1.9 vs 1.9 h), t1/2 (1.3 vs 1.4 h) and Ke (0.67 vs 0.67 h-1), respectively. AUC0-t, [formula in text] and Cmax were tested for bioequivalence after log-transformation of plasma data. PK parameters with 90% confidence interval (CI) of test/reference ratio based on ANOVA analysis were 0.961 approximately 1.135 for AUC0-t, 0.968 approximately 1.144 for [formula in text] and 0.951 approximately 1.117 for Cmax. CONCLUSIONS PK parameters with 90% CI were within the bioequivalence range of 80 - 125% of FDA statistical limit. Therefore, both omeprazole formulations were bioequivalent during fasting state in these healthy Korean male volunteers.