SUMMARY l. "Surveys were made in 1954 to 1958 to determine the geographical limits of the radioactive contamination from the tests in the central Pacific Ocean. 2. Collections of biological samples and soils were made at one test site island 3. (Bikini) and ten "off-site" islands. The gross beta radioactivity decreased with distance from the test site; in 1956 and 1958 islands within a 130~ mile radius contained at least ten times as much radioac- tivity as the other islands. 4. tion The levels of radioactivity also were related to direcfrom the test site. In 1955 the islands ' contained high levels of radioactivity. Tarawa, distance to the southwest, amounts of radioactivity. . 5. In 1956 and 1958 800 miles southeast of the test site, low levels whereas Kapingamarangi, to the east contained very approximately the same contained significantly higher Department of Energy Historian’s Office ARCHIVES 06 ,1 5 03 9 b were the predominant and Rut03, 106_py,1 Zr?>-n radioisotopes present in the majority of the samples.