The recurrence of glucose intolerance was examined in 36 women with an index pregnancy complicated by gestational diabetes who received antepartum care at the same institution because of a subsequent pregnancy. Standard oral or intravenous glucose tolerance tests were used to document glucose intolerance or gestational diabetes. Twenty patients had gestational diabetes in the subsequent pregnancy, whereas one third of the patients tested did not demonstrate an abnormality of carbohydrate metabolism. The patients with consecutive pregnancies complicated by gestational diabetes were heavier and were delivered of heavier neonates than the patients who did not develop gestational diabetes again. Unlike the nondiabetic group, the patients who remained gestationally diabetic weighed significantly more in the subsequent pregnancy than in the index pregnancy. These results indicate that patients with gestational diabetes should be tested in subsequent pregnancies because of the impact of gestational diabetes on birth weight. However, these results also suggest that the glucose tolerance test may not be a reliable test for the detection of abnormal carbohydrate metabolism.