The protective effect of Anacardium occidentale aqueous extract against streptozotocin-induced diabetes was evaluated in rats. The rats were treated with 175 mg/kg of the extract per os, twice daily; beginning 2 days before streptozotocin (STZ) injection. A total of 3 days after STZ administration, there was a 48% increase in blood glucose level in pretreated rats, compared with a 208% increase in diabetic control rats treated with STZ alone. Furthermore, these pretreated animals presented no glycosuria, a normal weight gain and a non significant increase in food and fluid intake at the end of the treatment compared with the normal control. Diabetic control animals showed a positive glycosuria, body weight loss, a real polyphagia and polydypsia. These results indicate the protective role of Anacardium occidentale extract against the diabetogenic action of STZ.