To investigate the effect of phosphate binding on the progress of chronic renal disease, aluminium hydroxide was administered to rats with focal glomerular sclerosis experimentally induced by adriamycin over a period of 28 weeks (group ADR-AH). The clinical data were examined every 4 weeks and the renal histology at week 28 were compared to those in adriamycin-injected rats without aluminium hydroxide treatment (group ADR). Urinary protein excretion was less marked in group ADR-AH than in group ADR at weeks 8 and 12. Serum creatinine in group ADR started to increase at week 20 and continued to rise until week 28, while in group ADR-AH it increased less, the difference being significant. Serum phosphate was lower in group ADR-AH than in group ADR at weeks 8, 12, 24, and 28. Focal glomerular sclerosis and tubulointerstitial changes were observed in both adriamycin-injected groups regardless of aluminium hydroxide treatment at week 28, although these changes were much less severe in group ADR-AH. There were no differences in body weight and serum albumin between the two groups. We conclude that aluminium hydroxide could prevent the renal deterioration in focal glomerular sclerosis induced by adriamycin without affecting the nutritional state.