The value of maternal glycosylated haemoglobin (HBA1c) and fructosamine in the prediction of gestational diabetes is debated. One hundred high risk patients were grouped as normal, impaired glucose tolerance (IGT) and gestational diabetes mellitus, according to the WHO criteria, after 2 hours, 75 g oral glucose tolerance test (OGTT). Maternal HBA1c and fructosamine were measured at different gestational ages and at the start of labour. The aim of the study was to determine the most sensitive predictor of abnormal glucose tolerance. Maternal fructosamine was higher in gestational diabetics than in the other two groups, but the difference was not of statistical significance. The values for normal and IGT groups overlapped markedly. The fructosamine test sensitivity was 12.2%, specificity was 94.7% and predictability was 75%. Glycosylated haemoglobin was significantly higher in IGT and gestational diabetes mellitus (GDM) groups than in the normal group after 36 weeks of gestation. At 32 weeks or less the difference was not of statistical significance. As with fructosamine, there was a wide range of value that overlapped markedly, particularly between the normal and IGT patients. The HBA1c test sensitivity was 19.1%, specificity was 95% and predictability was 81.1%. This suggests that both HBA1c and fructosamine have very low sensitivity as predictors of gestational glucose intolerance.