290 CONARD ET AL. d/m/1 on the twenty-fourth day to 33 d/m/] in 1956, and then increasing to 137 to 370 d/m/I in 1957.7 Preliminary analysis of the 1958 data indicates that the Cs"activity in urine increased by a factor of 100 over the 1957 levels. (Two resi- dents of Utirik Atoll who had beenliving on their island since several months after its accidental contamination in the 1954 fallout had urinary Cs" activities of 11,653 and 3735 d/m/I in 1937.) As part of the 3-year postexposure survey, + of the Rongelap people were brought back to Argonne National Laboratory where a more direct measurement of the internally deposited y-ray-emitting radioisotopes was obtained (7). The most prominent y-ray emitter was identified as Cs”, and the presence of the neutron- induced radionuclide Zn®* was discovered. Analysis of the spectra indicated an average body burden of 0.02 ue of Cs"? and 0.03 to 0.07 ue of Zn® in the Rongelap residents. Two Utirik residents similarly measured had 0.22 and 0.41 ye of Cs!” and 0.482 and 0.229 ue of Zn (76). Comparison of spectra in various groups of people at Rongelap Atoll in 1958 shows that there is little difference between those exposed in the 1954 fallout and those not exposed. A small group of people who moved from a noncontaminated island to Rongelap island only 214 months previous to the present survey had less than one-half the Cs" level and less than one-third the Zn® level of the Rongelap residents. A group of 56 people who had beenliving until a month before the survey on a slightly more contaminated island about ten miles to the north showedslightly higher Cs!” peaks than the inhabitants of Rongelap Island. Because the 1958 data have not been subjected as yet to thorough analysis, quantitative statements regarding the body burdensare preliminary. On the basis of counts made with appropriate standards corrected for absorption and geometry, however, it is estimated that the body burden is 0.3 to 1.7 we of Cs"? and 0.1 to 0.8 ue of Zn®. (The body burden of the Rongelap people of Cs! at 1 day after exposure in 1954 is estimated as having been about 0.01 to 0.02 uc.) The spectra of whole-body y-ray activity seen in 1957 and in 1958 in one of the Rongelap residents exposed in 1954 are compared in Fig. +. In both spectra Cs! and Zn® are responsible for most of the y-ray activity, but the 1958 levels of both are much higher than those seen in 1957. An additional peak is seen at 1.6 Mev in the 1958 spectrum. This peak was a prominent feature of the background spectrum and has tentatively been ascribed to La'*. It is probable that the Ba'°-La!" isotopic pair resulted from fallout contamination from the 1958 Pacific test series. The ship containing the steel room was slightly contaminated before proceeding 7We are grateful to Col. James Hartgering (MC) USA, Maj. Kent T. Woodward (MC) USA, Lt. Ariel Schrodt of the Walter Reed Army Medical Center, Dr. John Harley, and Mr. Edward Hardyof the New York Operations Office of the U.S. Atomic Energy Commission, and Dr. Stanton Cohn of the Brookhaven National Laboratoryfor assistance in radiochemical analyses. “ be 394