twice the natural potassium-40 activity in man and about 1/300 of the recommended maximum allowable activity for cesium-137 in nonindustrial personnel. Although the fodine-131 excretion levels measured in these Nevada subjects represented only a short interval of time, the values were not remarkably different from 1!3! measurements during Operation Teapot, The highest 1 31 activity measured in our study group was in an Alamo resident, and was 1.7 percent of the "maximum permissible thyroid burden" (NBS HB-68 standards). Thyroid burden can be estimated crudely by assuming that 30 percent of the urinary activity represented thyroidal release at a rate of about 2 percent per day. The mean adult thyroid burdens of 1131 are then: Mercury: Alamo: Lincoln Mine: 5.6 x 10°" microcuries 1.5 x 10-3 microcuries 1.6 x 1073 microcuries certainly encountered in MLON investigations. Pertinent problems in investiga-— tion and management were reviewed with MLON representatives, and some general recommendations for management of similar situations were developed. Nineteen sixty-eight also saw the institution of a program for doing whole-body scans and counting among representative residents of the off-site area. This program has continued and, along with the studies of the Alaska natives, has in become one of the main methods of monitoring body burdens of radionuclides residents of the off-site area. Genetic studies and evaluation of chronic radiation injury have never been entered by the MLON. MLON investigations have generally concentrated on acute illnesses, or problems, and have always tried to make a positive diagnosis rather than simply stating "that is not radiation injury." In all the years of MLON investigation, we have yet to find a true case of radtation injury which could be attributed to radioactive fallout. The 1960s saw a marked increase in the use of radiation by industry and physicians, with a comparable increase in the possibility of a yadiation incident occurring. It was believed desirable to include all types of radiation emergencies in the training sessions of the MLON. Several investigators carried out studies of leukemia clusters and thyroid disease in certain areas of Utah and Arizona. The MLON participated in some of these investigations carried on in the sixties. One of these investigations concerned leukemia deaths in the area surrounding St. George, Utah. Rumors were circulating among the citizens that certain deaths, and particularly an increase in leukemia deaths in 1962, were due to fallout occurring from some 1955 tests. During those tests, one cloud was estimated to have given the residents of a small town near St. George about 5 rad total body exposure, with higher doses to the thyroid. Review of the vital statistics for the area did show a small peak of cases in that year (1962). This was a "peak" of three cases, whereas the average for several years preceding and subsequent to 1962 was less than one case per a year. Statistical evaluation indicated that if four cases had occurred, it would have been a statistically significant peak, but three was still within the statistical variation. We had also received some complaints of chronic anemia and thyroid nodules in residents in northern Artzona. Investigation produced no significant findings in this area. Cases investigated by MLON in 1968-69 had very strong psychiatric overtones. One such patient called the USPHS and/or the AFC every 24-48 hours. She was hospitalized on several occasions with the final diagnosis being chronic paranoid schizophrenia. This diagnosis was arrived at only after all possible causes (organic) of her symptoms had been eliminated. This MLON case presented a difficult, and different, investigative and management problem. Psychiatric illness is common in the United States and was 23 :