The objective of this study is to evaluate pharmacokinetic parameters, bioavailability of a potent HIV protease inhibitor, nelfinavir mesylate (NFV), following a single oral administration of 2 tablet formulations. A randomized, 2-way, crossover, bioequivalence study was conducted in 24 healthy male volunteers to compare 2 brands of nelfinavir 250 mg tablets, Nelfabiovir (Bakhtar Bioshimi, Iran) as test and Viracept (Roche, Germany) as reference product. Blood samples were collected at selected times during 12 h and plasma concentrations were determined with a sensitive and validated HPLC method involving a simple protein precipitation step. Individual pharmacokinetic parameters, t1/2, t1/2(abs), K, Ka, tmax, Cmax, Vd/F, Cl/F, AUC0-12 and AUC0- yen were determined from plasma concentration-time profiles for both formulations and were compared statistically. The analysis of variance (ANOVA) did not show any significant difference between the two formulations and 90% confidence intervals (CI) fell within the acceptable range, satisfying the bioequivalence criteria of the FDA. In vitro parameters of mean dissolution time (MDT) and time for 70% dissolution (T70) were also determined. There was no significant difference between these parameters for two dosage forms (p > 0.05). It was concluded that the two nelfinavir products are bioequivalent with respect to the rate and extent of absorption.