Selected features of 'nephrosclerosis' can be quantitated morphometrically in renal histology at autopsy. Specimens are available from Japan, Mexico, and the US (blacks and whites). Autopsies of men and women aged 15-79 years provided renal samples for paraffin sectioning. These were assembled in New Orleans for objective evaluation after standardized staining with PAS-Alcian blue and interspersion with each other. Obsolescence of glomeruli, interstitial fibrosis, fibroplastic intimal thickenings of arteries, and arteriolar hyalinization, as operationally defined, were measured by objective morphometry. Obsolescence of glomeruli and interstitial fibrosis displayed the expected correlation with arterial intimal fibroplasia, but failed to confirm any direct association with arteriolar hyalinization. Some of the variation of 'nephrosclerosis', within and between populations, cannot be fully explained by microvascular defects. Arterial intimal fibroplasia appeared to promote 'nephrosclerosis', in the sense of fibrous replacement of atrophied nephrons, but arteriolar hyalinization did not. Hyaline deposits in arterioles may offer little or no threat to the integrity of the affected nephrons. 'Nephrosclerosis' appears to be multifactorial; it may be, in part, a consequence of fibroplasia in microscopic arteries causing ischaemic injury to scattered nephrons, but may also be a confluence of basically separate conditions, only some of which are known.