Quinine dihydrochloride was given intravenously to 12 women with severe falciparum malaria in the third trimester of pregnancy. The initial dose consisted of 10 or 20 mg salt/kg over 4 h and was followed by 10 mg salt/kg every 8 h until patients were fit to swallow, when quinine sulphate tablets were given. Uterine activity showed little or no change despite rising quinine concentrations. Of 3 patients in labour, 2 proceeded normally while a third had a successful caesarean section for fetal distress. Late (type II) decelerations of the fetal heart rate were recorded in 6 patients before treatment but in most patients signs of fetal distress diminished as the maternal temperature fell. Hypoglycaemia and hyperinsulinaemia developed in 7 patients, in 2 before quinine was started. The important toxic effect of quinine in late pregnancy is not an oxytocic action but rather its capacity to release insulin.