This work depends on the estimation of atazanavir sulphate in bulk and pharmaceutical dosage form by UV-Spectrophotometry. This includes method development and validation. Validation is an important parameter which includes linearity, accuracy, precision, specificity, robustness and ruggerdness of atazanavir sulphate for the perticular method. Stability studies are also being performed such as hydrolysis, oxidation, photometry and dry heat. The stabilyty test gives a perfect idea for determining the stability of the drug in different environmental factors. The results are satisfying and comparative to others which are obtained form HPLC.