A simple, sensitive and accurate spectrophotometric method has been developed for the determination of mesalamine in pure and commercial dosage forms. The method is based on the reaction of mesalamine with sodium nitroprusside in the presence of hydroxylamine hydrochloride in alkaline medium to give a highly green colored species which absorb maximally at 703 nm. Beer's law is obeyed in the concentration range of 0.0-30 μg mL-1 with molar absorptivity = 2.0367104 L mol-1 cm-1. The average recovery is 103.0 % and relative standard deviation is less than 1.5 % (n = 6). The proposed method has been applied successfully for determination of mesalamine in commercial pharmaceutical products such as tablet and suppositories. There is no interference from the excipients.