The effect of hyperlipidemia on the progression of chronic renal failure was investigated in 104 chronic renal failure patients, aged 39.3 +/- 2.9 years. The follow up period was 4.1 +/- 2.9 years. The serum creatinine level was 2.1 +/- 1.1 (mean +/- SD) mg/dl at the beginning of study and increased to 8.7 +/- 4.4 mg/dl at the end of the study. The reciprocal serum creatinine concentration (1/Cr) was plotted against the observation time, and the slope was calculated. The absolute value of the slope was used as the progression rate of renal impairment. The progression rate was positively related to total cholesterol level or urinary protein score, while it was negatively related to total protein level. Without the influence of urinary protein score, the progression rate correlated with total cholesterol level. The result suggests that hypercholesterolemia may be an independent aggravating factor in the progression of renal dysfunction in chronic renal failure patients.