internal methane gas-flow counting chambers at the Laboratory of Radiation Biology in Seattle. Counts per plate were converted to disinte- grations per minute per gramof wet tissue by correcting for samale weight, geometry, backscatter and self-abeorption. For s more complete discussion of these procedures see Donaldson et al. (1953) Other tissues were treated similarly, with the exception of liver,in which case the whole organ was removed from each specimen. If a suf- ficient number of specimens of a single species was obtained, the tissues were treated separately as in the case of goatfish and halfbeak from Kabelle Island (see Table 1). Decay rates for radioactivity of tissues of fish collected in 1956 were calculated because there were indications that Rongelap Atoll was contaminated during the Redwing operation. Gamma spectra and total gamma counts were made on dried or ashea samples ina single channel, 50-pogition, automatic advance, trometer using a two-inch, well-type sodium iodide crystal. gamma spec- Chemical analyses were made by ion-exchange resin column and radiochemical cipitation techniques The radioactive isotopes contained in the separate fractions were identified by determination of the gamma energies, beta mass absorption studies using aluminum foil pre- and by Correction factors for converting beta and gamma counts to d.sintegrations per minute were calcu- tate Sy the ose of standarde Bf knows cee gies. toe Doe Om . o - a a a ae used are given by Lowman et al (1957)