Experimental studies on albino rats reported that leaf extract of Ocimum sanctum and Ocimum album (holy basil) had hypoglycemic effect. To explore further evidence we studied the effects of treatment with holy basil leaves on fasting and postprandial blood glucose and serum cholesterol levels in humans through randomized, placebo-controlled, crossover single blind trial. Results indicated a significant decrease in fasting and postprandial blood glucose levels during treatment with holy basil leaves compared to during treatment with placebo leaves. Fasting blood glucose fell by 21.0 mg/dl, confidence interval of difference -31.4 - (-)11.2 (p < 0.001), and postprandial blood glucose fell by 15.8 mg/dl, confidence interval -27.0 - (-)5.6 (p < 0.02). The lower values of glucose represented reductions of 17.6% and 7.3% in the levels of fasting and postprandial blood glucose, respectively. Urine glucose levels showed similar trend. Mean total cholesterol levels showed mild reduction during basil treatment period. The findings from this study suggest that basil leaves may be prescribed as adjunct to dietary therapy and drug treatment in mild to moderate NIDDM.