This study was designed to evaluate the bioequivalence of two formulations of alendronate (CAS 121268-17-5) 70 mg (test formulation, alendronate 70 mg tablets, vs. the reference formulation) in 80 healthy volunteers under fasting conditions. The trial followed an open, randomized, crossover design with a washout period of 28 days. Urine samples were collected up to 48 h post-dose, and the concentrations of alendronate were determined by HPLC. The mean Ae(0-48) was (mean +/- SD) 152.15 +/- 136.09 microg for the reference formulation and 150.37 +/- 126.20 microg for the test formulation, while the mean Rmax was 53.33 +/- 41.53 microg/h and 55.85 +/- 49.57 microg/h, respectively. No significant differences in pharmacokinetic parameters between the two formulations were found. The 90% confidence interval for the ratios of Ae(0-48) and Rmax of alendronate were within the acceptance range for bioequivalence trials. The results of the present study suggest that the test formulation is bioequivalent to the reference formulation. The analyses of truncated AURC to shorter times showed similar values, which were within the range of bioequivalence.