The purpose of this study is to compare the bioavailability (rate and extent of absorption) of two tansulosine 0,4 mg capsule formulations. An open, randomized, two-period crossover study with a seven-days washout interval was conduced in 32 healthy male volunteers. The plasma samples were obtained up to 72 hours after drug administration. A sensitive and specific LC-MS/MS method was developed and validated for the determination of tansulosine in human plasma. Bioequivalence between the products was determined by calculating 90% confidence intervals for the ratio of Cmax, AUC 0-72h and AUC 0--inf.