Two cases of fatal, acute-onset, insulin-dependent diabetes mellitus (IDDM) in children were diagnosed. Epidemiologic and serologic studies, as well as histologic analysis of pancreatic tissue in fatal viral infections, support the contention that a viral infection could cause beta cell destruction, leading to IDDM. The presence of nucleic acid sequences from viral agents considered to be potentially diabetogenic, specifically, cytomegalovirus and mumps, rubella, and coxsackie viruses, were investigated in the pancreatic tissues by reverse transcription followed by polymerase chain reaction (RT-PCR) and Southern blot hybridization. Total pancreatic RNAs extracted from five children who died from nondiabetic causes were included as controls. Viral genetic information from any of these four viral agents was not found. This result indicates that the acute IDDM in these cases was not due to a direct infection of pancreatic beta cells by any of the viral agents studied.