Heteropneustes fossilis were subjected to 41.89 mg L-1 of azadirachtin for short-term exposure (96 h), and 10.47 mg L-1 of azadirachtin for long-term exposure (28 days). The fish were sacrificed on 24, 48, 72 and 96 h in short-term and 7, 14, 21 and 28 days in long-term experiment. Corpuscles of Stannius (CS) were fixed on these time intervals. Corpuscles of Stannius remain unchanged till 72 h in short-term azadirachtin exposure. Accumulation of granules has been noticed in the AF positive cells at 96 h. The nuclear volume of these cells remains unchanged. The AF negative cells of CS of azadirachtin exposed fish exhibit a slight increase in their nuclear volume after 96 h. In long-term exposure the CS remain unchanged up to day 14. Increased granulation in the AF-positive cells has been noticed following 21 days exposure. Moreover, the nuclear volumes of these cells show a significant decrease. Heavy accumulation of AF-positive granules and few degenerating cells are also noticed at 28 day in azadirachtin exposed H. fossilis.