Background & objectives: This study was undertaken to evaluate the glycaemic potential of aqueous extract of Psidium guajava unripe fruit peel on blood glucose level (BGL) of normal and streptozotocin induced mild and severely diabetic rats as an extension of our previous work carried out on Psidium guajava ripe fruit peel. Methods: The aqueous extract of P. guajava unripe fruits was prepared. Male 6-8 wk old albino Wistar rats were selected for the experiments. Diabetes was induced by streptozotocin infection. Blood glucose levels were measured by glucose oxidase method. Antihyperglycaemic activity of the extract was assessed in mild and severely diabetic rats.