AbstractThe avian retroviruses—and probably other retroviruses as well—undergo a variety of recombinational events with relatively high efficiency. An understanding of the molecular basis of these events should provide insight into the important biological properties these agents exhibit when they become integrated into somatic or germ‐line host cells, when they exchange genetic information among themselves, or when they transduce host cell genes. In this article we review molecular models for homologous recombination, against a background of the other types of recombination events that arc typical of these viruses. It seems probable that the retroviruses will provide useful models for analysis of a variety of DNA rearrangements known to occur in eukaryotic cells.