The present paper presents a morphometric study of the evolution of the glomerulus in Adriamycin-induced focal and segmental glomerulosclerosis in the rat over 32 weeks. The morphometric parameters studied generally varied significantly when the groups treated with Adriamycin were compared with controls. Glomerular area and perimeter showed an irregular pattern and finally ended up with values similar to those of the control group. Glomerular capillary tuft area and perimeter were always significantly greater in Adriamycin-treated groups than in controls. The mesangial area of treated animals increased over the study period in comparison with that of controls. While the total number of cells in the glomerular capillary tuft had an irregular pattern, the proportion of cells in relation to glomerular capillary tuft area was significantly lower in treated animals than in controls.