The clearance of Captopril (SQ 14225) was examined in six hemodialysis patients, using a newly developed method for the determination of Captopril in blood. At 30 minutes after the start of hemodialysis, the clearance of Captopril was 80 +/- 14.2 ml/min, whereas that of creatinine was 123.4 +/- 8.8 ml/min and that of BUN was 144.1 +/- 7.2 ml/min. The blood concentration of Captopril was found to be lower when taken in a postprandial state than in a fasting state.