-~64 omprehensive review of a year ago, we described our observations ng the very high incic<nce of chromosomal anomalies in this patient ad been studied in grzat detail. We published these observations (5) e first American pubLication of its kind several years ago. In those es we found that a hich incidence of anomelies 6% years after the 1 total of 475 millicuries of 1131, With the very extensive experience romosomal preparation and interpretation by Dr. Macintyre and his atory personnel, it seemed appropriate to carry these observations er and look for anomalies in individuais who had received doses of 15 millicuries of 1133 as treatment for hyperthyroidism. In the mean observations have been reported by others who used one or two ob- tions on each patient rather than a series to prove unquesticuably a change had taken place and to observe a sequence of changes. It een our policy to make multiple cultures from a series of 8 to 12 es of blood following a treatment dose of 1131, Two years ago we completed studies on a total of 6 patients given moderate therapeutic doses of 1131 for hyperthyroidism, but ‘n- nately, the full series of cultures was not always complete cn each nt. Some cultures failed and in two instances, the large number cf al control observations were not fully acceptable. From the meager on these patients, it appeared that there was a slight rise in Lies, Continuation of the work was limited at that time because of age of personnel on our own staff and on Lr. Macintyre's staff. g the last year we have resumed these studies with the. participation | graduate student who is addressing himself to this problem. We have ec in the past year assembled information on an additional 8 patients. xperimental design has been as follows: btained before any 1131 is given. Samples of blcod for cuiture Sufficient blood is obtained so multiple cultures will be available to clearly establish an inci malies before the radiation is given. Subsequently, samples of are obtained for culture at 1, 4, 10, and 24 hours, and 2, 3, 7 ys. The large battery of observations on the kinetics of the 31 2 patient are also carried out (as they have been described earlier 2port for estimating whole body radiation). Because all series of 3gome counts are done as complete un‘nowns, the results of most of observations are not yet identified, because study of slides is »gress. In at least two instances, where the observations on the 3 is comlete, it appears that chromosomal anomalies are being pro~ at a just significant level. It will require a considerably larger ° of patients and probably several years to obtain enough data to ge ar answer to this issue. In the more recent studies, non-radicacti ceatment) serum is obtained from the patient and stored to be used tc re the serum fin cell cultures) that bears 1131 when the nlood is drawy. xing the serum in the culture eliminates any radiation effect that occur while the culture is being incubated. The fact that the t's own hlood bearing some of the therapeutic dose was used in our periments was an objection to our original experimental design. It be argued that under the former conditions some radiation might be ined by the cells during culture rather than be sustained only. .? the cells were withdrawn from the patient. The background of de~- 1 studies to determine the radiation exposure in these treated patiests ‘or the chromosome studies is adding to our total number of patients 1d in great detail for purposes of ultimate relationship to effects ryroid.