A simple, precise and accurate difference spectroscopic method has been developed for the estimation of balsalazide in bulk and in pharmaceutical dosage form. The proposed method is based on the principle that balsalazide can exhibit two different chemical forms in basic and acidic medium that differ in the absorption spectra in basic and acidic medium. Since the drug was freely soluble in distilled water, a stock solution (1 mg/mL) was prepared with distilled water. Further dilution was made by using 0.1 M sodium hydroxide and 0.1 M hydrochloric acid separately. The maxima and minima in the difference spectra of balsalazide were at 460 nm and 354 nm, respectively. Difference in absorbance between these maxima and minima was calculated to find out the amplitude. This amplitude was plotted against concentration. Beer’s law is valid in the concentration range of 2-20 μg/mL. The results of analysis have been validated statistically and by recovery studies.