This volume attempts a synthesis of recombination and DNA repair by analyzing possible requirements of complex repair reactions and matching the known recombinational enzymes into the recombinational repair pathways. The work classifies serious DNA lesions, traces the evolution of recombinational repair models, introduces the concept of synapsis as the essence of recombinational repair, and discusses the biochemical properties of RecA protein. It also analyzes the prokaryotic pathways of recombinational repair and compares the prokaryotic paradigm with what is known about recombinational repair in eukaryotes.