Erythrocyte intracellular sodium [Na]i and potassium [K]i concentrations, maximum specific ouabain binding (OBmax), and Na+, K+ ATPase-dependent (ouabain-sensitive) rubidium influx (OSRb influx) were measured in women with pregnancy-associated hypertension (P-AH, pre-eclampsia) and compared with values for normotensive women in the third trimester of pregnancy. OBmax was significantly lower in women with P-AH compared with normotensive pregnant women, with a trend to higher [Na]i. There was a significant (p < 0.001) inverse relationship between OBmax and [Na]i. Although mean values for ouabain-sensitive rubidium influx in buffer were slightly lower in women with P-AH, this difference was not statistically significant. Lowest values were observed in women with proteinuric P-AH. There was no inhibition of OSRb influx by homologous plasma in groups of women with any severity of P-AH. Such inhibition was seen only in normotensive women with peripheral oedema. P-AH is associated with an abnormality of cellular Na+, K+ ATPase, but this appears to be an intrinsic abnormality and not due to the effect of a circulating factor inhibiting pump function.