Endogenous retrovirus-like sequences that are homologous to the multigenic murine and Syrian hamster intracisternal type A particle (IAP) genes can be detected in very few copies in the Chinese hamster (CH) genome. They were cloned from a CHO gene library and two recombinants, harboring the major IAP-like DNA genes characterized by Southern blot hybridization after DNA digestion with several restriction enzymes. The IAP DNA inserts of the two clones analyzed were 4.70 and 8.04 kb respectively, allowing us to construct a physical map of our Chinese hamster clone that represents an almost complete IAP element.