Saquinavir (SAQ) mesylate (CAS 149845-06-7) is a potent inhibitor of the HIV-1 protease indicated in combination with other antiretrovirals for the management of HIV-1 infection. The objective of this study was to compare rate and extent of absorption and to assess the bioequivalence between a new pharmaceutical equivalent tablet formulation containing 500 mg of SAQ mesylate and the innovator film coated tablet formulation. A randomized, single-center, open-label, two-treatment, two-sequence, three-period, replicated crossover bioequivalence study in 40 healthy male subjects was conducted. All subjects received 100 mg ritonavir (CAS 155213-67-5) twice daily for a run-in period of 3 days before treatment. Dosing was separated by a wash-out period of 14 days. Blood samples were collected over 72 h and plasma levels of SAQ were determined by a validated HPLC/UV assay. The 90% confidence interval (CI) of the ratio of the geometric means for log-transformed C(max), AUC(last) and AUC(inf) values were used to assess bioequivalence using the equivalence interval of 80-125%. Point estimate and 90% CI of the ratios of C(max), AUC(last) and AUC(inf) values were 94.9 (80.9-111.3), 97.4 (82.4-115.4) and 97.4 (82.5-115.0), respectively. Both treatments exhibited similar tolerability and safety. It was concluded that the new pharmaceutical product was bioequivalent to the innovator.