Replication-defective adenoviral vectors are widely used for gene transfer into mammalian cells. We show here that these vectors are also useful for delivering genes to chick embryos. Cells of many tissues expressed Escherichia coli beta-galactosidase following infection in vitro or in ovo with a recombinant adenoviral vector carrying this reporter gene. Labeled cells were morphologically normal and integrated normally into host tissues. Moreover, cells labeled in neural crest and somites subsequently migrated along normal paths. However, restricted subsets of cells were infected in some tissues at some stages, suggesting complex control of adenoviral infectivity and/or expression.