Puromycin aminonucleoside (PAN)-nephrotic rats show high plasma renin, low plasma angiotensinogen (Angt), and increased urinary excretion of renin and Angt. In this work, we studied the effect of captopril on urinary excretion of total protein, renin, and Angt for 25 days after PAN injection. Captopril had no effect on total protein urinary excretion; however, captopril did enhance the urinary excretion of renin and did decrease the urinary excretion of Angt. This seems to be due to the fact that captopril magnifies the increase in renin and the decrease in Angt in the plasma of PAN-nephrotic rats.