INTRODUCTION In this. revised edition of Chicago Sunshine Bulletin No. 12 are presented all gr90 concentration data obtained by the University of Chicago Project Sunshine group for the period December 1, 1955 to termination of the work in August 1956. For cumlative results to December 1, 1955 see Chicago Sunshine Bulletin No. ut 1. Results for samples assayed by the EE. A. Martell, "Project Sunshine Bulletin Number 11", December 1, 1955, Secret; AECD-3763, Jarmary 1957.6 Nuclear Science and Engineering Corporation, Pittsburgh, Pennsylvania, under subcontract, are included and are designated by the letter "P" following the Chicago Laboratory number (iee., CL xxx-P). This revised report includes all results and discussion contained in the original version of Chicago Sunshine Bulletin No. 12, August 1, 1956 plus additional results submitted to the Division of Biology and Medicine, United States Atomic Energy Commission in a letter report, "Chicago Sun- shine Results, Final List", dated August 3, 1956, Data of the last two colums, Table 6, pages 27 and 28, have been corrected to take into account the difference in ratio of available Sr7° to available calcium in the clectrodialyzed sample as compared with the original soil. is substantial for calcareous soils. The correction A new result is reported for the Brawley, California soil, CL 1127, (page 4, this report), establishing a lower maximum level of Sr% for this arid area. The data for all biological samples and soils are presented in units of 1/1000 of the occupational tolerance dose of sr% for an average man of 1000 grams total body content of calcium. Thus the "Sunshine Unit" equals 1/1000 microcuries of Sr?0 per kilogram of calcium or 2,2 disintee grations per minute of sr70 per gram of calcium.