Renal cortex in 15 cases with Itai-itai disease was morphometrically examined, i.e. the cross-size of tubuli in the renal cortex was measured using a color image analyzer (Olympus CIA-102) and the ratio of preserved urinary tubuli occupying renal cortex was calculated by means of the point-counting method. The former and the latter decreased gradually together as atrophy of kidney advanced. However, their decrease was stopped at about 60 g of kidney weight and it was inferred to be the limit of histopathologic changes of the kidneys with Itai-itai disease. Comparing the cross-size of the tubuli of the outer cortex area [= S(o)] with one of the inner cortex area [= S(i)], changes were more marked in S(o). This revealed that the outer cortex area was more sensitive to Cd intoxication and it was more affected by systemic atherosclerosis than the inner cortex area. It was concluded that when atrophy of kidneys as seen with Itai-itai disease was extremely progressing, decreases in the number and volume of tubuli in the cortex usually occurred at the same time and in a regular manner.