IMAMURA, M., YAMAUCHI, H., NAKAJIMA, Y. and SHIN, S. Improved Radioimmunoassay of Cholecystokinin (CCK) Using OAL-656 by Ethanol Extraction of Human Plasma. Tohoku J. Exp. Med., 1993, 170 (1), 53-58 In the radioimmunoassay of human plasma cholecystokinin (CCK) using an antiserum OAL-656, it has been difficult to get stable fasting values as well as prominent postprandial increase. Therefore, we tried to extract human plasma with ethanol before the radioimmunoassay, and could solve these problems, that is fasting concentrations became stable (16.7±2.5pg/ml) (mean±S.D., n=9), and CCK concentrations were augumented promptly after feeding and were kept at higher levels for a certain period. - cholecystokinin; human plasma; radioimmunoassay; OAL-656; ethanol extraction