SECTIONI PHYSICAL DECAY OF SAMPLES FROM ENIWETOK ATOLL IN 1952 INTRODUCTION Previous decay studies (UWFL-53) of the biota and other materials from the Marshall Islands have covered periods up to nearly three years following the detonation of atomic testing devices. The earliest curves (AECD-3446:27) were for oyster, XE-19, and ovary of damselfish, XE-40, whose slopes from 20 to 800 days were -1.6. Decay of 83 samples from Rongelap Atoll (UWFL-42:46) over a period of from 38 to 500 days following March 1, 1954 averaged -1. 4. Coconut milk was most unusual among these, having a decay rate of only -0. 24, Decay data for samples collected in 1952 offer the most comprehensive picture of long-term decay trends that may now be contributed from studies by the Laboratory of Radiation Biology. proximately seven years is involved. These samples number 102, of which 96 were from Eniwetok Atoll collected within Mike test, A period of ap- 10 days after the 6 were within 10 days pre-Mike and would be referred to the Greenhouse series. In addition there were 2 Nevada sand samples col- lected on November 29, 1951, related to the Uncle-Jangle atomic tests, making a total of 104 decay curves. -l-