ABSTRACT The objective of Project 2.1 was to determine gamma exposures versus distance from the point of detonation of various high-yield devices. The following types of dosimeters were used as gamma-radiation detectors: photographic, quartz-fiber, chemical, and phosphate-glass. Correction factors were applied to compensate for the nonlinear speetral response of the dosimeters, when necessary, and for station shielding. All detectors were calibrated with Co® sources. Photographic dosimeter readings were accepted as the most reliable on a statistical basis and were used as bases for most of the curves plotted. Photographic dosimeter film-badge service and Co" calibration facilities were provided to other projects as requested. Initial-gamma radiation was measured at a series of stations located at about 1 to 4 miles from ground zero. Mechanisms were installed at some of these stations to shield the detectors from residual radiation. An analysis of the data indicates that the initial-gamma exposure at 3 miles from Cherokee, Zuni, and Navajo was about lr. Consequently, initial-gamma radiation was oflittle military significance to exposed personnel as compared to thermal and blast damage resulting from high-yield devices. The curves in this report vary from those published in TM 23-200 (Reference 1). Thefield data falls below predictions at longer ranges and is greater than predicted at shorter ranges. This difference between predicted and field data increases with increasing yield. For fallout residual-gamma radiation measurements, instrument stations were located on almost every island of Bikini Atoll at distances where neutron-induced activity was entirely negligible. The amount of residual-radiation exposure was a function of the fission yield, Residual-gammaradiation data points are mapped in this report for Shots Zuni, Flathead, Navajo, and Tewa.,