SUMMARY The Problem Fallout sampling by Project 2.63 at Operation REDWING was conducted by groups of similar instruments and each group was located on the periphery of @ special wind-shielded platform designated as the standard platform. The amount of fallout collected by the instruments within each platform showed considerable variation and it is likely that these variations were caused by the effects of wind flow about the platform. Therefore it is necessary to correlate the sampling variations with the air-flow characteristics above the platform and with the properties of the prevailing winds. Another objective of this study is the determination of the equivalent ground value of the collections from platforms mounted on ships i.e., the value that would be collected by the earth's surface at the same location. To attain this objective the relationship between platform and ground sampling was needed. Findings Studies of the fallout collection data and the platform's air-flow characteristics showed that the amounts of fallout collected around a platform vary symmetrically with respect to the wind direction in a single-wind system or to a correlated reference wind direction in a multi-wind system. For both wind systems the amount of fallout collected in the upwind part of the platform was lower than that of the downwind section. The sampling variation within each platform can be defined by the use of certain parameters. The value of these parameters were determined from the properties of the collection curve describing the sampling variation around a given platform. Only the sampling relationships between platform collection and ground collection of the single-wini system could be described. It was not possible to determine the equivalent ground values of shipboard collections because of the lack of fundamental data or platform-ground sampling relationships. iii