farther to the south, and was less under the center of the plume than was Rongelap. The largest group of inhabitants was on Utirik, which is the farthest of these atolls from Bikini; andthis group apparently received the lowest doses. These estimates were based primarily on average readings of radiation survey instruments, taken at about 1 meter above ground, several days after evacuation of the residents. An approximate energy spectrum was derived from spectroscopic measurements on the fall-out material, and adjustment ofthe assumed (ground plane) geometry and air attenuation. The chronology of the exposure was inferred from survey meter and film badge readings on Rongerik, visual identification of the arrival of the plume over Ailingnae and Rongelap, and other considerations. Re-estimation of the absorbed dose to the servicemen on Rongerik, taking into account the chronology of the exposure, personnelactivities and assumed protection factors (when inside buildings), rate of decay of fall-out radiation intensity, and other data, suggested a population average total body dose equivalent of 0.37 Gy (37 rad). The revised estimates are shown in Table 1; they are based on free air ionization estimates. The authors of the detailed study suggested a conversion factor for average dose equivalent from exposure in air to be 27.1 Gy C' kg (0.7 rad/R) (34). They also assumed that the servicemen spent more time indoors than did the authors of the original dosimetry. When these factors are taken into account, the two estimates are in agreement, and a value of 0.3-0.4 Gy (30-40 rem) is established. The protection factors for the Marshallese, however, are not as great. As noted above, the houses ofthe island residents were made oflight, natural materials and offered little shielding. Also, the residents, being unaware of the radiologic hazard, spent mostoftheir time outdoors. Therefore, the adjustment of their whole-body exposures to dose equivalent by the 27.1 Gy C’ Kg (0.7 rad/R) factor probably is reasonable, but further reduction by a factor of about 2.0 for shielding is not warranted. This would suggest whole-body external dose equivalents from early exposure to be 1.2 Gy (120 rad), 0.48 Gy (48 rad), and 0.10 Gy (10 rad) for the Rongelap, Ailingnae, and Utirik residents, respectively. Oneestimate of external doses has been attempted through purely theoretical treatment of the device yield, meteorologic dispersion (35), etc. The calculated results are not in agreement aurement and analyses carried out for the atolls. A lack of available 20