A marked difference in the dissolution rate between two brands of nimodipine tablets was observed using a newly developed dissolution medium of pH 4.5 acetate buffer containing 0.05% sodium dodecyl sulfate (SDS).However,when pH 4.5 acetate buffer containing 0.3% SDS was used as dissolution medium, which was specified in the British Pharmacopoeia(BP)2000 edition,the dissolution results of the both brands conformed to the BP requirements and no significant difference in dissolution was observed.The dissolution data obtained for two commercial brands of nimodipine tablets indicate the superiority of the proposed system as a discriminatory dissolution medium for nimodipine tablets.The relative bioavailability of the two brands of nimodipine tablets was determined in healthy adult volunteers after a single dose in a randomized crossover study. Plasma concentrations were determined by a liquid chromatography-tandem mass spectrometry method. Statistical comparison of the AUC0-T, AUC0–∞, Cmax, and Tmax indicated a significant difference in the two brands of nimodipine tablets.