SLIDE 41 External exposure measurements. In April 1975, BNL personnel initiated an external survey of Bikini Atoll in order to obtain information concerning the ambient external radiation levels resulting from the mid 1950's weapons testing program and to make dose equivalent determinations for the individuals living in the surveyed area. From 1975 to 1977, measurements were made to provide sufficient information on the external exposure received by the Marshallese people. The equipment used were a Reuter Stokes environmental radiation monitor, model RSS~111, and a Baird~Atomic scintillation detector consisting of a sodium iodide detector (2.5 cm in diameter by 3.9 cm in length) connected to a ratemeter readout. Portable survey meters were used to help locate gross changes in the external exposure rate. Lithium fluoride thermoluminescent dosimeters were left on Bikini Island for several months and retrieved in December 1975, Environmental exposure levels were assessed via the RSS~ll1. The Nal gamma spectrometer was used by us to determine the photon energy distribution and to compensate for the nonlinearity in the RSS-111 instrument response.