Herbal medicines have been used since the dawn of civilization to maintain health and to treat diseases. Diabetes mellitus is one of the leading cause of death in many developed countries. The incidence of diabetes is increasing at an alarming rate in India. It was estimated that India which had 19.4 million diabetes in 1995 is expected to register a near threefold increase by. Many plants reported to be useful for the treatment of diabetes mellitus in ayurvedic medicine, are being tested for their hypoglycemic activity in experimental animals Lagerstroemia flos- reginae is one such plant commonly found as shade trees in Kerala. In Ayurveda both root and leaves are used in the treatment of diabetes. The main objective of this study was to assess the antidiabetic effect of the alcohol extracted leaves of Lagerstroemia flos- reginae in alloxan induced diabetic rats in terms of controlling blood glucose level, lipid profile, bilirubin, uric acid in serum and lipid peroxides and glutathione in the liver of the experimental animals. The present study has been undertaken to observe the protective effect of the active constituents of Lagerstroemia flos- reginae leaf extracts against alloxan induced diabetes in experimental animal model. The activity of the active constituents was compared with Daonil -a standard drug.