This triple-blind, placebo-controlled clinical trial was conducted to determine the effect of the vitamin E on fasting blood sugar (FBS), serum insulin, and glycated hemoglobin (GHb) in type 11 diabetic patients (NIDDM). A total of 100 patients, with no complications, aged 20-60 years old were chosen from those consulting the Isfahan Social Security Service Diabetes Clinic and divided randomly into two treated and placebo groups, and matched for age, sex, level of education, and occupation. The treated and placebo groups were given vitamin E tablets (200 IU/day) and placebo respectively. Serum vitamin E, total cholesterol (TC), triglycerides (TG), FBS, insulin, and GHb were measured at the beginning and at the end of the study (a period of 27 weeks); FBS, GHb and insulin levels were also determined several times during the period. Blood lipids and FBS were measured using the ELAN 2000 autoanalyzer at the Isfahan Cardiovascular Research Center, while for measuring insulin the enzyme-linked immunosorbent assay (ELISA) method was used; GHb was determined calorimetrically (thiobarbituric acid), and for vitamin E measurements the Hansen and Warwick method was used, by which the vitamin E was determined fluorometrically. The findings of this study show no effect of vitamin E supplementation in the patients: GHb did not change appreciably, FBS was reduced nonsignificantly (-4.3% in the treated group vs. -14.0% in the placebo group, p < 0.05). In the case of insulin, no increase was seen; instead, a decrease was observed (slightly more than 17% in the two groups, p = 0.15). No changes were observed in the levels of blood lipids. It was concluded that a daily vitamin E supplement of 200 IU for a period of 27 weeks does not affect insulin, GHb, or FBS in type II diabetic patients. However, since this antioxidant vitamin is beneficial in other ways in these patients, it would seem justified to recommend its use. Certainly, more extensive research is necessary to draw definite conclusions.