consisted of radiological surveillance of a network of 19 monitoring stations on populated islands within a 2,000 mile radius of Christmas Island. Air samples were collected on populated islands out to about 1,000 miles from the test zone. Samples of soil, vegetation, fruits, water and marine life were collected on the populated islands of the area before testing began and repeated sampling was made after the testing period to determine whether changes in the level of radioactivity had occurred in the area. The 19 sampling stations were divided into (1) primary stations, (2) secondary stations, and (3) background stations. The primary sta- tions (Christmas, Fanning and Washington) were manned by USPHS officers with equipment and sampling techniques to document all forms of environmental radioactivity. The secondary stations (Canton, Malden, Penrhyn/ Tongarev, Palmyra, Midway, Johnston Island and French Frigate Shoals) were outside the danger area and were designed to document air concentration and external radiation background. These stations were operated by Task Force Project Groups and Weather Groups. Background stations on Tutuila, Rarotonga, Wake Island, Kwajalein Atoll, Tongatabu and Viti Levu were operated by Task Force Project Groups or Weather Groups and on Nuku Hiva and Tahiti by French personnel. The purpose of the back- ground stations was to document external radiation background and changes in background levels if they occurred. A USPHS laboratory was established in Honolulu, Hawaii to support the Off-Site Rad-Safe program. Facilities, equipment and personnel were available for radiochemical analysis of air, precipitation, water, milk, food and soil. ee if