Background: Neonatal dried blood spots (Guthrie cards) have been used to demonstrate a prenatal origin of clonal leukemia-specific genetic aberrations in several subgroups of childhood acute lymphoblastic leukemia (ALL). One hypothesis suggests that an infectious agent could initiate genetic transformation already in utero. In search for a possible viral agent, Guthrie cards were analyzed for the presence of 3 newly discovered polyomavirus Karolinska Institutet polymavirus (KIPyV), Washington University polyomavirus (WUPyV), and Merkel cell polyomavirus (MCPyV). Methods: Guthrie cards from 50 children who later developed ALL and 100 matched controls were collected and analyzed by standard or real-time polymerase chain reaction for the presence of the VP1 region of KIPyV, WUPyV, and MCPyV, and the LT region for MCPyV. Results and Conclusions: DNA from KIPyV, WUPyV, and MCPyV was not detected in neonatal blood samples from children with ALL or controls. Prenatal infections with these viruses are not likely to be etiological drivers for childhood leukemogenesis.