Adenoviruses, types 2 and 12 induce amplification of SV40 DNA sequences in cells of the SV40-transformed human newborn kidney cell line, NB-E. Similarly, integrated hepatitis B virus DNA sequences in the human hepatoma cell line, PLC/*PRF/5, and bovine papillomavirus (BPV) DNA sequences in BPV-transformed mouse cells (ID13) are amplified by adenovirus infection. Thus, similar to herpes group or vaccinia viruses or DNA damaging agents, adenoviruses are able to mediate selective DNA amplification in addition to their reported mutagenic and chromosome damaging effects. The role of amplification of integrated viral DNA sequences in development and progression of specific tumors (e.g. hepatocellular carcinoma) remains to be determined.