Adult male rats were exposed to 4 and 10 Gy of whole-body gamma radiation, and several metals of plasma were studied on 1st, 3rd and 6th day after exposure. Lethal radiation increased plasma calcium initially with subsequent diminution, while plasma magnesium decreased initially in both groups, becoming normal on the 6th day post exposure. Plasma iron in 4-Gy exposed rats diminished on 3rd day, while the same in 10-Gy exposed animals increased initially and then decreased. Both groups of animals exhibited significant diminution of plasma copper and ceruloplasmin from the 3rd day post irradiation. Plasma monoamine oxidase (MAO) was enhanced from 1st day post exposure in 10-Gy exposed rats, which persisted still 6th day. Liver monoamine oxidase was significantly diminished from 1st day after exposure in lethally exposed rats, while spleen monoamine oxidase, after initial increase was normalised on 6th day post irradiation.