Fifty hypertensive untreated outpatients (34 women, 16 men), with stage I and II essential hypertension, were studied in comparison to 50 age- and sex-matched controls with similar life-styles. Total cholesterol triglycerides, LDL-cholesterol, VLDL-cholesterol, and HDL-cholesterol were measured by enzymatic methods, and apolipoproteins AI, AII, B, CII, CIII and E by RID. The results showed significant differences between hypertensives and controls respectively in triglycerides (135.2 +/- 73.9 versus 90.2 +/- 33.8, P less than 0.01) and VLDL cholesterol (26.7 +/- 14.8 versus 17.7 +/- 6.6, P less than 0.01) while no significant differences were observed in total, LDL and HDL cholesterol. Significant differences between the two groups were also observed in apolipoproteins, particularly in apo AI (130.0 +/- 28.2 versus 144.9 +/- 27.9, P less than 0.05), apo AII (32.9 +/- 10.2 versus 39.6 +/- 11.4, P less than 0.01), apo CII (4.0 +/- 2.6 versus 5.4 +/- 2.9, P less than 0.05) and apo E (5.0 +/- 1.8 versus 4.3 +/- 1.8, P less than 0.05), while no significant differences were observed in apo B and CIII values. The results suggest that in untreated hypertensive patients alterations in the apolipoproteins profile are present which, in part, may be responsible for the elevated incidence of cardiovascular disease, independently from the blood pressure values.