The possible interrelationships between the erythrocytic transport systems of Na+ (Na+/K+ pump, Na+/K+ cotransport, Na+/Li+ countertransport, Na+ passive permeability) and the plasmatic lipids (cholesterol, triglycerides, HDL, LDL, apoprotein A1, apoprotein B) were studied in 42 normotensive subjects with different forms of hyperlipoproteinaemia and with a negative familiarity for arterial hypertension. In subjects with hypercholesterolaemia (hyperlipoproteinaemia II A and II B) an elevated activity of the Na+/K+ pump was noticed, while in subjects with hypertriglyceridaemia (type IV) an increase in Na+ passive permeability and Na+/Li+ countertransport with a lower level of intraerythrocytic Na+ was shown. A negative correlation was observed between the total efflux of Na+ and Na+/K+ pump and the levels of cholesterol (r = -0.43, p < 0.04 and r = -0.41, p < 0.05) and the apoprotein B/A ratio (r = 0.42, p < 0.05 and r = -0.50, p < 0.01). A negative correlation was also noticed between the Na+/K+ pump and the levels of apoprotein B (r = -0.41, p < 0.05). The Na+/K+ cotransport appeared inversely correlated with the levels of HDL cholesterol (r = -0.42, p < 0.05), while the Na+ passive permeability was negatively correlated with the levels of LDL (r = -0.43, p < 0.04) and positively correlated with the plasmatic triglycerides (r = +0.54, p < 0.01). Such data show that the plasmatic lipids can influence the systems of transmembrane ionic transport of Na+ and play an important role also this way, in cardiovascular pathology.