A new viral sequence (IDDMK(1,2)22) similar to the human endogenous retrovirus (HERV)-K10/K18 subfamilies has recently been isolated from the culture supernatants of leukocyte-infiltrated islets from two patients who died at the onset of type 1 diabetes. It was claimed that this endogenous retrovirus is expressed in patients with type 1 diabetes but not in healthy control subjects, suggesting an important role of the retrovirus in beta-cell-specific autoimmunity that results in type 1 diabetes. However, despite exhaustive attempts involving identical and expanded methods of detection, we did not observe the IDDMK(1,2)22 viral sequence in genomic DNA, lymphocyte, or plasma RNA in any subject. Therefore, we believe that the viral sequence is not derived from an endogenous retrovirus and that a role for the retrovirus in the pathogenesis of type 1 diabetes must be reconsidered.