Kidney samples obtained at autopsy were evaluated for nephrosclerosis by quantitatively measuring the severity of intimal fibroplasia in the interlobular arteries and counting the number of hyalinized arterioles. Most cases were obtained from the coroner and had violent causes of death; subjects with cardiovascular diseases were excluded. Blood pressures in Health Survey data were obtained from published sources. Measures of nephrosclerosis in 365 black and white men and women in age groups 25 to 34, 35 to 44, and 45 to 54 yr were examined by three-way Analysis of Variance (ANOVA). Blacks exceeded whites in fibroplasia at all ages and in both sexes; this excess was paralleled by mean blood pressure in all comparisons. White women were not different from white men in fibroplasia; black women significantly exceeded black men at all ages. Women had lower blood pressures than men when matched for age, race, and fibroplasia; the average magnitude of this difference was 5.5 mm Hg. Since women are known to have as much hypertensive disease as men after age 50 yr, it seems possible that the arterial fibroplasia seen in young women may represent progression toward the hypertensive state, even through blood pressure does not reveal the equality of the sexes in this respect until after menopause. Hence, in women arterial fibroplasia is seen to precede a later rise in blood pressure. Arteriolar hyalinization was greater in men than in women but did not differ significantly between races. Hyalinization did not consistently follow blood pressure in comparisons between subgroups of subjects.