The purpose of the present study was to evaluate the bioequivalence of two pioglitazone HCl tablets, $Actos^{TM}$, tablets (Lilly Korea. Ltd., Korea) as a reference drug and $Piros^{TM}$, tablets (Reyon Pharm. Co., Ltd., Korea) as test drug, according to the guideline of Korea Food and Drug Administration (KFDA). Twenty-four healthy male Korean volunteers received one tablet containing pioglitazone HCl 15 mg in a $2{ imes}2$ crossover study. There was a one-week washout period between the doses. Plasma concentrations of pioglitazone were monitored for over a period of 36 hr after administration by using a high performance liquid chromatography-tandem mass spectrometry (LC-MS/MS). The area under the plasma concentration-time curve from time zero to 36 hr ($AUC_{0-36hr}$), maximum plasma drug concentration ($C_{max}$) and time to reach $C_{max}$ ($T_{max}$) were complied from the plasma concentration-time data. Analysis of variance (ANOVA) test was utilized for the statistical analysis of the parameters using logarithmically transformed $AUC_{0-36hr}$ and $C_{max}$. The 90% confidence intervals of the $AUC_{0-36hr}$ ratio and the $C_{max}$ ratio for $Piros^{TM}$/$Actos^{TM}$. were log 0.8753-log 1.1286 and log 0.8669-log 1.1734, respectively. These values were within the acceptable bioequivalence intervals of log 0.80-log 1.25, recommended by KFDA. In all of these results, we concluded that the $Piros^{TM}$. tablet was bioequivalent to the $Actos^{TM}$. tablet, based on the rate and extent of absorption.