Using a non-invasive cardiac output monitor (Bo-Med NCCOM 3-R7), we have compared cardiovascular responses, degree of haemodilution and incidence of nausea during extradural Caesarean section in healthy non-labouring mothers given either ephedrine 17.5 mg and 3% Dextran 70 7.5 ml kg-1 before delivery (group A) or volume loading with Dextran 15 ml kg-1 without infusion of ephedrine (group B). Smallest systolic arterial pressures before delivery were 114 (SEM 4) mm Hg (group A) and 105 (5) (group B). There were no significant differences between the groups in mean arterial pressure, heart rate, systemic vascular resistance or central venous pressure, while cardiac output increased more with the ephedrine infusion (P less than 0.05). Haemodilution was 8% in group A and 16% in group B at the time of delivery. Ephedrine infusion was associated with a smaller incidence of nausea (P less than 0.01). Umbilical arterial pH values were not different between the two groups. We conclude that infusion of ephedrine, combined with low volume colloid administration, is a safe alternative to more extensive colloid volume expansion for control of hypotension and provides effective prophylaxis against nausea during extradural Caesarean section in healthy non-labouring mothers.