In view of suggested anti diabetic potential, effect of aqueous and cold extracts of Terminalia catappa Linn (Combretaceae) leaves, on fasting blood sugar levels and serum biochemical analysis in alloxan-induced diabetic rats was investigated. All the extracts of Terminalia catappa produced a significant anti diabetic activity at dose levels of 1/5th of their lethal doses. Concurrent histological studies of the pan-creas of these animals showed regeneration by aqueous and cold extracts which were earlier necrosed by alloxan.