Angiotensin II is critical in pre-eclampsia pathogenesis. In addition, microRNA-155 regulates angiotensin II type 1 receptor expression. We have explored the function of microRNA-155 in pre-eclamptic pregnant women. Human umbilical vein endothelial cells were isolated and cultured from healthy puerperant women and pre-eclampsia patients. The cells were transfected with a mature microRNA-155 plasmid. The effect of microRNA-155 was assessed by Northern blotting, in situ hybridization, quantitative real-time PCR, immunofluorescent staining and Western blotting. In addition, activation of extracellular signal-regulated kinase 1/2 was assessed by co-immunoprecipitation and Western blotting. Severely pre-eclamptic pregnant women expressed less mature miR-155 compared to healthy pregnant women. In addition, angiotensin II type 1 receptor expression decreased substantially in healthy cells and miR-155-transfected cells compared to miR-155-mutant-transfected cells and cells from pre-eclamptic patients. Mature miR-155 reduced angiotensin II-induced extracellular signal-regulated kinase 1/2 activation. In conclusion, endogenous mature miR-155 expression may be an important contributor to the pathogenesis of severe pre-eclampsia.