The activity of erythrocyte glyceraldehyde-3- phosphate dehydrogenase (G3PD) was studied in normal individuals, type 1 diabetics and insulin treated diabetics. The activity of G3PD was found to be significantly increased in diabetic state, however, insulin treatment restored the activity to normal level. The percentage of G3PD bound to the red cell membrane was also significantly high in diabetics. It is suggested that G3PD plays a regulatory role in diabetic red cell in maintaining the normal ATP level.