A 12-month prospective study was carried out in 120 Chinese patients with gestational diabetes who were found to have persistent carbohydrate intolerance at 6 weeks postpartum. The 75 g OGTT and WHO diagnostic criteria were employed for both antepartum and postpartum assessment. By 12 months, persistent carbohydrate intolerance was found in 13.3% of the patients only, 6 patients were diabetic while 10 had impaired glucose tolerance. Of those whose carbohydrate tolerance reverted to normal, 85% did so within the first 6 months. The clinical variables were analysed by multiple discriminant analysis using the logistic model. Five prognostic variables which were predictive of persistent carbohydrate intolerance at 12 months were identified. In order of decreasing predictive value, these included a high fasting glucose during pregnancy and at the first postnatal visit, a high antepartum 2 h blood glucose, the requirement of insulin during pregnancy, and a high postpartum 2 h blood glucose. Macrosomia, gestational age at diagnosis and a family history of diabetes were not predictive of persistent carbohydrate intolerance. Multiparity, maternal age and body mass index were of marginal significance only. The fitted logistic model provides a mechanism to estimate the probability of persistent carbohydrate intolerance. Such information will be helpful in patient counselling and in the efficient planning of postpartum medical follow-up.