Catechins, polyphenolic compounds belonging to flavanoid family, have been reported to posses insulin-like properties and their antidiabetic actions have also been documented. Recently catechins have received much attention as strong anti-oxidative agents. Since oxidative stress has been implicated in the development of diabetic complications and GSH plays an important role in protection against oxidative damages, we have studied the in vitro effect of (-)epicatechin and insulin on the reduced glutathione content in normal and type 2 diabetic erythrocytes. The GSH content was significantly lower (p < 0.001) in type 2 diabetic patients as compared to normal individuals. In vitro insulin treatment (10(-9) M) resulted in increase in the GSH content in both normal and type 2 diabetic erythrocytes. (-)Epicatechin (1mM) also resulted in an increase in erythrocyte GSH content in both normal and type 2 diabetic erythrocytes. Insulin gave a pronounced dose-responsive effect: maximum increase in GSH content at physiological hormone concentration and a lower increase at higher and lower insulin concentrations. (-)Epicatechin did not show a similar dose-responsive effect. Although the exact mechanism by which (-)epicatechin causes elevation of erythrocyte GSH is not clear nevertheless this finding may have important therapeutic implications. A higher content of dietary flavanoids may thus protect diabetic patients against long-term complications.