The carbohydrate metabolic status in 10 women with previous non-insulin-dependent diabetes in pregnancy and in 8 control subjects was evaluated prospectively during a 6-month treatment period with an oral contraceptive containing 30 micrograms ethinyl estradiol and 150 micrograms levonorgestrel. An oral glucose tolerance test was performed before treatment and after tablet intake for 2 and 6 months. At each test, plasma values of glucose, insulin, and glucagon were measured. Before treatment the non-insulin-dependent diabetic patients demonstrated significantly increased glucose values and decreased insulin values as compared with the values of the control subjects. During treatment they displayed a small but significant rise in plasma insulin values. The glucose tolerance, however, remained unaffected in both groups during the study period. No change in body weight or blood pressure was observed. The results indicate that hormonal contraception of the low dosage type may be administered to women with previously impaired glucose tolerance in pregnancy without any deterioration of the glucose metabolism post partum.