The present paper presents data obtained from analyses of Pacific Ocean tune collected in 1967, - 60 occurrence o£ Co and 137 Cc s as well as 1968 and 1969. 55 s . The a8 Fe in tuna is discussed. MATERIALS AND METHODS Tissues of both light and dark muscle from tuna caught between July 1967 and June’ 1969 were obtained at the Tokyo port The samples were oven-dried at the National Institute of Health, Department of Food Control, | of landing of the Japane e fishery. Tokyo, under the supervision of Dr. Seattle for analysis. T. Kawabata and shipped to Dates and locations of catches were obtained from the vessels' logs. The species sampled were yellow- fin (Taunnus albacares), bluefin (Thunnus thynnus), and big eye (Thunnus chesuc). The samples were redried in Seattle and prepared for analy- sis by gamwaa-ray spectrometry by compressing the tissues into standard counting geometries. After analysis for gamma-emitting radionuclides, portions of the samples, usually 20 grams per sample, were taken for analyses of iron-55 and stable iron, Guplicate. in The light muscle and dark muscle obtained from the fish were both analyzed for iron-55, but since the of the two tissues were similar, iron-55 greater in the Gark muscle, te ~ soe los ~ 7 ee lentiy chcained w as pans and stable 9) nad Chi a) ? uu a ; ° © oO ry’ the specific activities iron as would concentrations were only the dark muscle from fish analyzec, art