Current views of DNA repair and mutagenesis in the yeast Saccharomyces cerevisiae are discussed in the light of recent data, and with emphasis on the isolation and characterization of genetically well-defined mutations that affect DNA metabolism in general (including replication and recombination). Various "pathways" of repair are described particularly in relation to their involvement in mutagenic mechanisms. In addition to genetic control, certain physiological factors such as "cell age", DNA replication and the regulatory state of the mating-type locus, are shown to also play a role in repair and mutagenesis.