A novel stability-indicating reversed phase high-performance liquid chromatographic assay method was developed and validated for quantitative determination of tamsulosine hydrochloride in bulk drugs and in pharmaceutical dosage form in the presence of degradation products. An isocratic, reversed phase HPLC method was developed to separate the drug from the degradation products, using an Ace5-C18 (250×4.6 mm, 5 μm) advance chromatography column, and 10 mmol L-1 methanol and water (70:30 v/v) as a mobile phase. The detection was carried out at a wavelength of 280 nm. The tamsulosine hydrochloride was subjected to stress conditions of hydrolysis (acid, base), oxidation, photolysis and thermal degradation. Degradation was observed for tamsulosine hydrochloride in base, in acid and in 30% H2O2. The drug was found to be stable in the other stress conditions attempted. The degradation products were well resolved from the main peak. The percentage recovery of tamsulosine hydrochloride was from (98.65 to 100.01%.) in the pharmaceutical dosage form. The developed method was validated with respect to linearity, accuracy (recovery), precision, system suitability, specificity and robustness. The forced degradation studies prove the stability indicating power of the method.