Objective To investigate leucocyte Na+/H+ exchanger isoform 1 activity in postpartum pre‐eclamptics.Design Exchanger isoform‐1 activity and intracellular resting pH were established in leucocytes isolated from two study groups.Sample Leucocytes isolated from 10 women who had had pre‐eclamptic pregnancies more than five months postpartum, and from 10 age‐matched normotensive women who were more than five months postpartum.Setting Hypertension Clinic, Antenatal Assessment Area, Leicester Royal Infirmary.Methods A well validated technique involving flurometry using a pH sensitive dye (BCECF‐AM) was performed to determine exchanger isoform‐1 activity and intracellular pH. Determination of exchanger isoform‐1 protein abundance was performed by western blotting. Exchanger isoform‐3 protein abundance was examined to rule out the possibility of activity due to this particular isoform.Results Intracellular pH was significantly lower in the postpartum pre‐eclamptic group (7.11 +/‐ 0.02), compared with the postpartum normotensive controls (7.33 +/‐ 0.04; P<0.001). Exchanger isoform‐1 efflux rate (in mmol/L/minute) was significantly higher in the postpartum pre‐eclamptic group (35.91 +/‐ 3.1), compared with the postpartum normotensives (23.94 +/‐ 2.0; P= 0.005). Exchanger isoform‐1 protein density was established to be similar among the two subject groups. No exchanger isoform‐3 protein was identified by western blotting.Conclusion Our results suggest that elevated exchanger isoform‐1 activity is an important finding in women who have suffered from pre‐eclampsia. This increased activity is not due to an increase in exchanger isoform‐1 protein abundance or the presence of exchanger isoform‐3.