Tumor necrosis factor-α (TNF) is a multifunctional protein hormone that contributes to host defense and perinatal immunologic development. Dysregulated TNF production, however, occurs during the pathogenesis of autoimmune diseases and may be inherent to their development. In animal models of autoimmunity, dysregulated TNF synthesis has resulted from mutations in TNF gene regulatory sequences, specifically those sequences involved in translational control of TNF gene expression. In this study, we have determined whether mutations in the TNF translational control sequences are present in pediatric patients with type I diabetes mellitus and connective tissue diseases. Blood samples were collected from 48 patients with connective tissue diseases, 32 patients with diabetes, and 29 controls. A 250-bp fragment of the translational control sequences present in the TNF 3'-untranslated region was amplified by the polymerase chain reaction, sequenced, and analyzed relative to the published TNF sequence. In this study, all patients and controls exhibited the normal sequence, with no insertions or deletions in the translational control motifs. We conclude that polymorphisms in the TNF 3'-untranslated region occur infrequently, if at all, in patients with diseases examined here.