The etiology of differentiated thyroid cancer (DTC) is unknown, but there are several risk factors including female sex, exposure to ionizing radiation, and previous malignancy. Recent studies have suggested a role for altered oncogene expression [e.g. c-myc, ras, and papillary thyroid cancer gene (PTC)] in DTC. None has been abnormal in the majority of patients although PTC may be present in more aggressive tumors. To seek supporting evidence for the possible role of such genetic factors in pediatric patients with DTC, we reviewed 120 records of patients with DTC from the Department of Defense (DoD) Centralized Tumor Registry. All were diagnosed between 1953-1994 and ≤ 21 yr of age. Of these, 100 were papillary, 19 follicular, and 1 mixed papillary/follicular. Of note, 88.3% were Caucasian, 4.2% Black and 7.5% of other races. Although the exact racial distribution of all DoD pediatric patients is not known for this time period, we did compare this distribution to that of 18,832 representative DoD pediatric admissions for 1995. This was 69% Caucasian, 23% Black, and 8% other races and differed significantly from that of patients with DTC diagnosed in the 1990s (86.5% Caucasian; CI 73.6-93.9%, p<0.0005). When the data were stratified by decade of diagnosis, the incidence of DTC was greater in Caucasians from each decade. These differences support the hypothesis that there are genetic determinants in the etiology of DTC in children.