Children with insulin-dependent diabetes mellitus (IDDM) suffer from a chronic autoimmune beta cell destruction of unknown origin, maybe due to superantigens or retroviral endogenous genes. Recently, a novel endogenous retrovirus designated as IDDMK 22 was proposed to encode for such a candidate autoimmune gene in type 1 diabetes. We therefore analyzed the expression of IDDMK 22 genes in peripheral blood leukocytes and plasma from 55 healthy children and 55 diabetic children including 11 patients with acute disease onset. In our study we applied an improved quantitative and highly specific real-time PCR assay. In contrast to previous data obtained by conventional PCR. IDDMK 22 gene expression did not differ between diabetic and nondiabetic individuals. For this reason, we propose that IDDMK 22 is an ubiquitous endogenous retroviral element in the human genome but not a candidate autoimmune gene for IDDM, especially in childhood-onset disease. Real-time PCR proved to be a highly sensitive and specific method for detection and quantitation of very low amounts of mRNA and will thereby be useful regarding the special demands in pediatric studies dealing with very low amounts of specimen.