and plankton and to identify the principal radioisotopes in the samples. The USS Collett (DD730) was provided by the U. S. Navy for the work and the survey included thirty-nine collecting stations spaced on a fifty-mile grid (Fig. 1) in the area bounded by 10°00'N and 13°20'N and 160°10'E and 166°00'E. In addition to the apove named radioisotopes, a neutron-induced radioisotope, tungsten-185, not previously found at the test site by the present authors, was detected in high amounts in some of the samples. The gamma peak of wi85 was first observed in gamma spectra made aboard the USS Collett on total plankton samples; however, the isotope was not positively identified ' until chemical separations were made. In this paper the methods used to establish the identity of the nuclides are described as well as the pattern of distribution of the isotope in plankton and other samples. MATERIALS AND METHODS The physical and chemical properties of w85 were used to identify the isotope. w85 decays principally by the emission of a beta particle of an energy of approximately 0.43 MEV. A gamma component (2.4 per cent) with an energy of 0.055 MEV is also emitted and can be readily identified in the gamma spectra.