I. Young Rongelapese exposed to fallout (175 rads external dose plus 600 to 1400 rem internal), March 1, 1954, when they were: 1 to 8 years of age - Total - 19 1. Currently normal by clinical and biochemical tests, (11%) 2. Currently hypothyroid with minimal nodularity. Responding satisfactorily to oral thyroid hormone therapy, (167) 3. Have undergone surgery because of nodular thyroids; histologic diagnoses of adenomatous goiter and Hurthle cell tumor. 11 (587) Responding satisfactorily to oral thyroid hormone therapy. 4. Recent development of nodules in the thyroid; will go to Brookhaven for evaluation and possible surgery. (None of six Ailinginae children exposed to external dose of 70 rad have shown thyroid dysfunction.) II, Surviving adult Rongelapese exposed to fallout: Total - 34 TiI, 1. Papillary carcinoma removed surgically at age 41. No recurrence, Taking oral thyroid hormone therapy. 2. Small nodule at age 40 which disappeared under oral thyroid hormone therapy. 3. Rough mass in one lobe at age 36; will go to Brookhaven for evaluation and possible surgery. Surviving adult Ailinginae people exposed to fallout (70 rads external dose); Total - 8 1, Adenomatous goiter removed at age 45, Recovered and on thyroid therapy but died of influenza in 1968, (16%)