When dose data were not available or incomplete, or when there was reason to believe that the data did not adequately characterize the actual exposure, alternative approaches were used as circumstances warrantad. All approaches had in common the investigation of individual or group activities and their relationship to the radiological environment. First, if it was apparent that personnel were not present in the radiological environment and had no other potential for exposure, then the assigned dose was zero. Second, if some members of a group had film badge readings and others did not-~and if all members had a common relationship with the radiological environment --then doses for unbadged personnel could be statistically calculated. Third, where sufficient badge readings or a common relationship to the radiological environment did not exist, dose reconstruction was performed. This involved correlating a unit’s or individual’s activities with the quantitatively determined radiological environment. The three approaches are summarized as follows: 1. Activities of an individual or his unit were researched for the period of participation in an atmospheric nuclear test. Unit locations and movements were related to areas of radiation. If personnel were far distant from the nuclear detonation(s), did not experience fallout or enter a fallout area, and did not come in contact with radioactive samples or contaminated objects, they were judged to have received no dose. 2. Film badge data from badged personnel may have been used to estimate individual doses for unbadged personnel, provided that the group of badged participants had common characteristics and potential similar to the unbadged personnel for radiation exposure. Then, using proven statistical methods, an estimated dose equal to 95-percent probability that the actual exposure did not exceed such estimate was assigned to unbadged personnel. This practice ensured that unbadged personnel were assigned doses that were considerably higher than the average or mean dose of the group. 3. Dose reconstruction was performed if film badge data were unavailable for all or part of the period of radiation exposure, if film badge data were partially available but could not be used statistically for calculations, if atypical activities were indicated for specific individuals, or if other types of radiation exposures were indicated. In dose reconstruction, the conditions of exposure were reconstructed analytically to determine the radiation dose. Such reconstruction was not a new concept; it is standard scientific practice used by health physicists when the circumstances of a radiation exposure require investigation. The underlying method was in each case the 166 ‘£3