1. Hypoglycaemia is a serious complication of falciparum malaria, especially in pregnant patients. To investigate malaria-associated changes in glucose metabolism in pregnancy, steady-state [6,6- 2 H 2 ] glucose turnover and clearance were measured in 10 women (eight with uncomplicated falciparum malaria and two with vivax malaria at 16–30 weeks gestation) before treatment, after intravenous quinine infusion (patients with falciparum malaria) and in convalescence. 2. Admission basal plasma glucose concentrations were higher than those in convalescence [median (range); 4.8 (3.6-7.0) versus 4.0 (3.6-4.6) mmol/l, P = 0.02], and there was a significant fall during initial quinine treatment in patients with falciparum malaria [5.0 (4.3-7.6) to 3.6 (3.2-5.4) mmol/l, P <0.01]. Basal plasma insulin levels were comparable at presentation and follow-up ( P = 0.35) and rose an average of only 2 m-units/l during quinine infusion ( P <0.05). Pretreatment glucose turnover rates [3.37 (2.57-4.16) mgmin −1 kg −1 ] were comparable with those found in a previously reported study of non-pregnant severely ill patients [3.22 (2.12-4.82) mg min −1 kg −1 , n = 11] and correlated significantly with the admission parasitaemia ( P <0.025). In the eight patients with falciparum malaria, there was a significant fall in turnover during intravenous quinine infusion [3.42 (238-4.16) to 2.66 [1.94-3.94) mgmin −1 kg −1 ] whereas clearance did not change significantly. In convalescence, turnover values showed a wide scatter, although the highest values (3.34-4.33 mgmin −1 kg −1 ) were in patients studied within 4 days of presentation (two patients) or with pre-eclampsia (one patient); values for glucose clearance were consistently higher than those at presentation ( P = 0.004). 3. Given the simultaneous plasma glucose and insulin concentrations, these results suggest that the combination of pregnancy and severe malaria may result in greater initial glucose requirements than in severely ill but non-pregnant patients, that there is a largely insulin-independent reduction in glucose production and utilization during quinine therapy which may partly reflect attenuated parasite glycolysis, and that early convalescence in pregnant women may be associated with higher glucose utilization than that in non-pregnant patients.