‘ater & The interior exposure rate is that which was observed at the center of the dwelling at a height above the floor of three feet or at contact with the floor. Both values were. investigated. The exterior exposure rate used in the above equation was the arithmetical average of the four external exposure rates measured around each dwelling site. Exposure rate reduction factors for each dwelling are indicated in Table 2 for the floor and three foot height situations, The measure- ments are stratified according to each aspect of construction encountered. The average interior exposure rate at floor level and at three feet in the center of the dwellings (exluding those filled with masonite and those having only a slab) is about 11 uR/hr. CONCLUSIONS On Bikini Island, exposure rates present from radioactivity remaining post nuclear testing are reduced within the concrete dwellings by a significant amount. Upon completion of the housing construction effort, an exposure reduction factor of about 50% may apply. This is about what was expected provided materials of construction contained low levels of radioactivity, Even greater reduction can be expected when the housing area is covered with one to two inches of coral gravel as has beén. recommended. Depending on the occupancy time for residents of these houses, total exposure to external radiation can be expected to be reduced accordingly. ACKNOWLEDGEMENT The authors wish to recognize the role of the Department of the Interior and particularly the Office of Trust Territories of the Pacifi