Diabetes mellitus is a metabolic disorder which has affected several millions of population all over the world. It is characterized by an excess of sugar in the blood and urine, hunger, thirst and gradual loss of weight. Insulin is a hormone which regulates the carbohydrate and triacylglyceride metabolism through its action at several sites and facilitates the entry of glucose accumulation in the blood. Insulin also stimulates the synthesis of glucokinase and moderates the degree of gluconeogenesis. In the diabetic patient, there is an aberration in the functioning of insulin. Prior to the 1950s, control of diabetes was based entirely on insulin therapy. Unfortunately, some patients developed complications and thus need for some other therapy was realized. Presently control of NIDDM relies on compounds from two classes--sulphonylureas and biguanides. Although these drugs are widely accepted as being efficacious in treating some diabetics, they are ineffective in many others. Consequently, testing of many chemicals and plant extracts has continued. The object of the present paper is to bring up-to-date information on the hypoglycemic activity of plants, above all the plants occurring in our country, and those who se hypoglycemic activity has been scientifically documented in a more detailed way. Recent theories on the mechanism of action of these plants are also discussed.