- 33 - SUMMARY 1. Chemical separations by ion-exchange resin column and precipitation techniques were made on selected samples collected at the Eniwetok Test Site during the summer of 1958. The chemically separated radioactive isotopes were identified by determination of maximum beta energies, gamma energies, and half life. 2. The presence of wi85 and other gamma-emitting isotopes on or in other samples from the Eniwetok Test Site and from the nearby populated atolis of Rongelap and Ujelang was determined by means of gamma spectrum analysis of whole samples. 3. wi85 first observed on plankton collected approximately 150 nautical miles northwest of Eniwetok, contributed up to 83 per cent of the total activity of the gamma-emitting isotopes in the sample. Plankton specimens contaminated by wi85 were taken in two other general areas, one approximately 90 nautical miles southwest of Eniwetok and another southeast of Bikini Atoll. Plankton taken outside these areas did not contain radiotungsten nor was it found in any plankton samples collected three weeks later in the same area.