During a 5 1/2-year period we saw 171 pregnant women with established non-insulin-dependent diabetes; 78 patients received oral hypoglycaemic drugs during the 1st trimester and 93 did not. The outcome of pregnancy in these two groups is compared. Only two major congenital anomalies were seen in the tablet-taking group and the number of abortions (4) was not excessive. The perinatal mortality (PNM) rate was initially high after large doses of chlorpropamide or metformin had been given during the 1st trimester, but this was clearly related to inadequate diabetic control in later pregnancy. Among the last 50 of the total of 75 viable infants whose mothers received oral drugs early in pregnancy, the PNM rate was 40/1 000. We conclude that modern oral hypoglycaemic drugs are safe and useful, not only during later pregnancy but also during the 1st trimester, provided excellent control of blood glucose levels is achieved.