Introduction Enewetak Atoll is one of the Pacific atolls used for testing of U. S. nuclear weapons. A large-scale radiological survey was conducted in 1972-1973 (EN73) to determine dose estimates for future inhabitants (NA75). Those whole body dose estimates are due primarily to energetic gammas, primarily from 1376, and 6006, A subsequent radiological survey of Bikini Atoll (another former. U. S. nuclear weapons testing site) indicated, however, that perhaps as much as 25% of the total external exposure rate is due to beta or low energy gamma radiation (GU75). In August, 1976, beta and gamma dose measurements were made at Enewetak Atoll to determine the beta or low energy gamma contribution to the total external dose, its dependence on ground cover, and the impact on external dose estimates for future inhabitants. Enewetak Atoll is located in the northern part of Micronesia about 3,800 km southwest of Honolulu. Forty islands on a coral reef ring a lagoon of approximately 40 km diameter (Figure 1). The largest islands and consequently most important for future villages and agriculture, are Enjebi (Janet) and Bokambako (Belle) in the northern half of the atoll, and Enewetak (Fred), Medren (Elmer), and Japtan (David) in the southern half. Most of the more than 40 nuclear weapons tests were conducted in the northern region of the atoll, with approximately half tested over the lagoon or ocean areas and the remainder tested on several northern islands. major radioactive contamination and hence radiological northern half of the atoll. 5004292 Therefore, the impact was to the