The plasma glucose and insulin responses to oral glucose were studied in 44 women who had previously had gestational diabetes, but had reverted to normal glucose tolerance. Twenty were White, 14 Black, and 10 Asian. A group of race-, age- and weight-matched controls was also studied. Fasting values of glucose and insulin did not differ significantly between the study group and controls. During the 2 h 75-g OGTT the White and Black previously gestational-diabetic women had similar plasma glucose values to their controls, while the Asian previously gestational-diabetic women had significantly higher glucose values at 30 min (9.2 +/- 0.6 (+/- SE) vs 7.1 +/- 0.3 mmol l-1, p less than 0.02) and at 60 min (8.6 +/- 0.8 vs 6.2 +/- 0.4 mmol l-1, p less than 0.02). Compared with their race-matched controls, the White previously gestational-diabetic women had significantly lower insulin values at 60 min (median 41 range 2-91) vs 56 (15-118) mU l-1, p less than 0.05), and the Black previously gestational-diabetic women had lower values at both 30 min (17 (4-116) vs 53 (22-197) mU l-1) and 60 min (36 (4-148) vs 99 (12-169) mU l-1, p less than 0.05). The insulin values were similar during the OGTT in the Asian previously gestational-diabetic women and their controls.(ABSTRACT TRUNCATED AT 250 WORDS)