Antihypertensive therapy has been shown to slow down the progression of chronic renal failure. Angiotensin converting enzyme inhibitors and calcium antagonists have been emphasized as the agents with the most protective effect. Our previous study showed that captopril slowed down renal function deterioration in the early course of adriamycin (ADR) nephropathy in spontaneously hypertensive rats (SHR). The present study was undertaken with the aim to examine morphologic changes associated with that slower renal function deterioration. Adult (24 weeks) female SHR were randomly divided into the following groups: the control group (n = 12) was given tap water to drink; the adriamycin (ADR) group (n = 25) was treated with ADR; the ADR-captopril (ADR-C) group (n = 27) was treated with ADR and thereafter with captopril (60 mg/kg/day). Rats were sacrificed at weeks 6, 12 and 18 and histologic analysis was semiquantitatively performed. In the control group the glomeruli exhibited only minor changes at the end of the study. In the ADR group slight glomerular mesangial hypercellularity appeared in the sixth week and progressed in focal and segmental sclerosis. Some glomeruli showed segmental proliferation and increased fibrular matrix of a tuft adherent to a fibrocellular crescents. In the ADR-C group, glomeruli with a slight increase of mesangial matrix were seen at the end of the sixth week, mesangial hypercellularity developed until the end of the sixth week, mesangial hypercellularity developed until the end of the 12th week and segmental glomerulosclerosis until the end of the study. Semiquantitative analysis revealed that the mean semiquantitative scores for mesangial expansion and glomerular sclerosis were significantly lower in ADR-C group than in ADR group throughout the study. We concluded that captopril slowed down mesangial expansion and reduced the development of glomerular sclerosis.