AbstractDiabetes mellitus was induced in male Wistar rats by the administration of streptozotocin (STZ, 45 mg/kg, s.c. on 2 consecutive days). Hyperglycaemia and superoxide dismutase activity of pancreatic islet cells was assessed on days 7, 14, 21 and 28, following STZ administration. In two other groups, shilajit (50 and 100 mg/kg, p.o.) was administered concurrently for 28 days. STZ induced significant hyperglycaemia by day 14, which increased progressively on days 21 and 28. STZ also induced a decrease in pancreatic islet cell superoxide dismutase, which was apparent by day 7 and increased progressively, thereafter on days 14, 21 and 28. Shilajit (50 and 100 mg/kg, p.o.) had no discernibleper seeffect on blood glucose levels in normal rats but attenuated the hyperglycaemic response of STZ from day 14 onwards, though only the effect of the higher dose was statistically significant. Similarly, both the doses of shilajit reduced the STZ‐induced decrease in superoxide dismutase activity from day 14 onwards, the effect of the lower dose being statistically insignificant. The findings confirm earlier observations that STZ‐induced hyperglycaemia may be the consequence of a decrease in pancreatic islet superoxide dismutase activity, leading to accumulation of free radicals and damage of the β‐cells. Shilajit attenuates both these effects of STZ possibly by its action as a free radical scavenger. The findings support the postulate that shilajit can prevent maturity onset diabetes me