The purpose of this study was to evaluate the efficacy of chromium supplementation as a treatment for gestational diabetes. Of 30 gestational diabetic women (20-24 gestational wk) recruited for study, 20 were randomized into two groups: 10 received 4 g/d/kg/body weight of chromium picolinate (4 g CrPic), and 10 received placebo. Ten additional women, matched for glucose intolerance and body mass index to the placebo group, received 8 g/d/kg/body weight of CrPic (8 g Cr). All baseline blood determinations and the 100 g glucose load were repeated after 8 weeks of supplementation in all three groups. At baseline, the three groups did not differ for insulin, C-peptide, or glucose levels at the fasting and 1 hr time point after the 100 g oral glucose challenge test. Three women in the 4 g CrPic group, one woman in the 8 g CrPic group, and four women in the placebo group failed diet and required insulin. After 8 weeks, the 4 g CrPic group had significantly lower glycosylated hemoglobin levels (HbA 1c ) compared to baseline (5.2 ยฑ 0.6% vs. 5.6 ยฑ 0.4%, respectively, P < 0.05), whereas the 8 g CrPic and the placebo groups showed no change in HbA 1c . After 8 weeks, the two CrPic-supplemented groups had significantly lower glucose and insulin levels compared to their baseline levels and to those of the placebo group. The 8 g CrPic group had significantly lower postprandial glucose levels than the 4 g CrPic group. In conclusion, CrPic supplementation for gestational diabetic women improves glucose intolerance and lowers hyperinsulinemia.