The recombination of DNA takes place by a multistep process involving numerous gene products. In the past year, studies using bacterial proteins have led to a number of significant advances in our understanding of the enzymes of recombination and of the reactions that they catalyze. Moreover, the identification of eukaryotic proteins that are structurally analogous to the principal bacterial recombination enzyme, RecA protein, suggests that the basic mechanisms of homologous pairing and strand exchange have been conserved through evolution from bacteria to man.