In Breathitt County, Kentucky, an Appalachian Mountain community, 1,267 children were examined to determine goiter prevalence. Matched pairs of 82 goitrous and nongoitrous children were reexamined six months later for family history, urinary iodine excretion, serum thyroxine, triiodothyronine, protein-bound iodine, thyrotropin, and thyroid autoantibodies. Goiter prevalence was 8.4%. Iodine deficiency was not found. Thyroid stimulating hormone levels were higher in the goitrous group. Microsomal autoantibody titers were elevated in 20% of the children with goiters vs 6% of controls (P less than .05). Fluorescent antibodies were associated with positive microsomal (P less than .01) but not with positive tanned RBC autoantibodies. Unexpectedly, on repeat examination, goiter was absent in 17 (21%) of the originally goitrous group, but was now present in 22 (25%) of the controls. We concluded that while evolving thyroiditis is common in Appalachian children, it does not explain all goiters in an area of abundant iodine intake and known familial goiter.