Serial measurements of glycosylated albumin (GAlb), glycosylated plasma proteins (GPP) and glycosylated haemoglobin (GHb) were performed by affinity chromatography throughout the course of pregnancy in 14 insulin-dependent diabetic women. In patients whose glycaemic control improved markedly during pregnancy, the concentrations of GAlb and GPP decreased by more than 50 per cent after four weeks of good diabetic control. By contrast, the rate of decrease in GHb levels in the same patients was significantly less and did not indicate a comparable improvement in glycaemia until 12 weeks after good diabetic control was established. Elevated concentrations of GAlb or GPP decrease much more rapidly than GHb concentration when diabetic control is improved; thus measurement of glycosylated proteins is a valuable adjunct to serial blood glucose monitoring in clinical circumstances such as diabetic pregnancy, where early confirmation of good diabetic control is important.