We have found that the replication of human adenovirus (Ad2) is restricted in multiple Chinese hamster cell lines including CHO and V79. The major site of restriction involves differential accumulation of late viral proteins as demonstrated by immunofluorescence assay and polyacrylamide gel electrophoresis with and without prior immunoprecipitation. Synthesis of fiber and penton base are markedly reduced, whereas others, such as the 100K polypeptide, are synthesized efficiently. This pattern of restriction is similar to that previously reported for Ad2 infection of several monkey cell lines; however, the restriction is more marked in the Chinese hamster cell lines. The restriction is most likely due to a deficient cellular function since stable cell hybrids between V79 or CHO and human cells are permissive for virus replication. By analysis of a series of hybrids with reduced numbers of human chromosomes, fiber synthesis was correlated with the presence of the short arm of human chromosome 3. More hybrids showed restoration of fiber synthesis than production of progeny virus, suggesting that more than one unlinked function is required for the latter.