whose thyroid doses ranged from about 400 to 5200 cGy, only 1 of 28 (4%) had the diagnosis of occult papillary carcinoma. If only those Rongelap individuals with doses less than 2000 cGy are analyzed, 1 of 13 (8%) had an occult carcinoma, and for those receiving over 2000 cGy the prevalence is 0%. Therefore, the high radiation dose received on Rongelap may have decreased rather that increased the incidence of the occult tumors. But a factor that renders any conclusion of questionable value is that in many of the surgical explorations the entire thyroid gland was not removed and subjected to the close histologic examination that has been used in most studies on occult papillary carcinoma prevalence. The Marshallese data may, therefore, underestimate the prevalence ofthese lesions, particularly in the multinodular adenomatousgoiters of the exposed Rongelap children. The combined number of occult papillary carcinomas and overt carcinomasin the Rongelap and Utirik groupsis virtually identical, being 7.0% in the former and 6.6% in thelatter: Rongelap Exposed persons Occult CA 86 1 Total CA Exposed/Total CA 6 7.0% Overt CA 5 8) Did thyroxine suppression decreage the incidence of benign and/or malignant nodulq in radiationexposed persons? Administration of thyroxin for he purpose of suppression of development of th bid nodules in Marshallese who had been living o Rongelap at the time of exposure was initiated 1965 shortly after the first thyroid nodules (Conardet al., 1967). The distributi¢ subsequently extended to include tho suppression. It is given to them onl indicated as noted below. Every six months a supply of tabiets is handed out to each exposed Rongelap person, whether or nd that person endocrinologic consultants who accompany the medical team during their work 1 the Marshall had thyroid surgery under the al Marshall Islands Medical Program,w or not, for replacement and suppregsion. Utirik 167 6 5 11 6.6% There are proportionally more carcinomas in the Rongelap group and more occult papillary carcinomas in the Utirik. One might wonder whether radiation exposure had the effect of inducing or hastening a change toward increasing virulence in the usually benign-acting "occult" lesions. However, such an interpretation does not take into account either the limitations on technique of histological examination of the thyroid mentioned in the preceding paragraph or the extensive thyroid injury in those in the Rongelap group whoreceived more than 2000 cGy to the thyroid. Frolund, 1984), and (4) a decrqa nodules but not malignant nodules (Fogelfeldet al., 1989). One study found that thyroxfne reduced the numberof recurrences in those whq had previously undergone therapy for papillary thyroid carcinoma (Schneider et al., 1986), although Fhe number of patients not. given suppressive thegapy was small. The timing of thyroxine prophylaxis may be an important factor in determiningits Effectiveness; if started some years after exposure ifs value may be lessened (DeGroot et al., 1983). Any conclusions derived from tlfe results of the The Rongelap group has been re suppression since 1965 but it compliance with this regimen is popr, estimated at no better than 50% (Adams et al, 1983). The suppression was not initiated untif 10 years after 23 3f