This paper describes a morphometric study of the evolution of tubulointerstitial nephropathy in adriamycin-induced focal and segmental glomerulosclerosis in Wistar rats over 32 weeks old. The earliest changes were located in the glomeruli. In the 10 week of the study, tubulointerstitial nephropathy appeared and, although the interstitial space increased after the 2nd week, this increase only became statistically significant after the 10 week. Proteinuria showed the highest correlation with the interstitial space, however, the interstitial space showed the highest correlation indices with the total number of glomeruli affected and to a lesser extent with adhesions to and thickening of Bowman’s capsul