OBJECTIVE: To examine microvascular endothelial cell function in vivo in pre-eclampsia. DESIGN: Iontophoresis of acetylcholine (Ach), which gives rise to endothelial cell dependent vasodilatation, and of sodium nitroprusside (SNP), which elicits vasodilatation independently of functioning vascular endothelium. SETTING: Södersjukhuset, Stockholm, Sweden. SUBJECTS: Ten pre-eclamptic patients, ten healthy pregnant women and ten healthy nonpregnant women were examined. MAIN OUTCOME MEASURES: The degree of vasodilatation following iontophoretic administration of Ach compared with SNP was recorded with a laser Doppler technique, the data being analysed on a personal computer. RESULTS: Both Ach and SNP administration resulted in marked vasodilatation; the magnitude of the vasodilatation was similar in the three groups of women. CONCLUSION: Following iontophoretic administration of endothelial cell dependent or independent vasodilatators, laser Doppler measurement of blood flow demonstrated no microvascular endothelial cell dysfunction in pre-eclamptic women.