The Pacific Incident On March 1, 1954 a 15 megaton! * thermonuclear shot designated as BRAVO, was fired on a reef extending from the Island of Namu located on the northwest part of Bikini Atoll, Figure 2 shows the estimate that I made of the pattern of fallout from BRAVO - expressed as the doses that persons who were out-of-doors, without shielding, could have received over a two day period following the initial appearance of the fallout. The doses shown over land areas were estimated from dose-rate readings by survey meters held at three feet above the ground, Doses over sea areas were extrapolations of land survey data and thus are much less certain. However, after constructing the "best fit"' isodose lines, I calculated from these data that the total quantity of radioactivity that was deposited within 400 miles downwind represented about 2/3 of the total amount produced by the detonation. This estimate is not in conflict with those made in subsequent years by others who were able to incorporate more data from later surface detonations, In addition to the "absolute" values shown in Figure 2, the relatively sharp gradients of the isodose lines, especially those across the main line of the fallout, are of interest to those concerned with the subject of this symposium, Of course, patterns of fallout will be strongly a function of the wind structure, DOE ARCHIVES