The manual consists of two main sections. The first includes the essential, sometimes laborious, procedures for handling yeasts, for inducing mating and isolation of hybrids, for inducing sporulation and isolation of single-spore clones, with some details of tetrad analysis, and including techniques and ancillary equipment for use of the micromanipulator. There are also proce dures for induction of mutants by physical and chemical agents, and for iso lation of particular types of mutants, such as to temperature sensitivity, for increased frequency of mutations, for mutations in the mitochondrial genome, both to the petite colonie form and to resistance to antibiotics, for mutations in that part of the yeast genome controlling the glycolytic cycle, and numerous others. Mapping of mutations is discussed briefly, though this aspect of yeast genetics is probably one which should not be undertaken until the investigator has gained a certain amount of experience in the field. How ever, as is pointed out in the pertinent part of the manual, the task of mapping has been tremendouslysimplified by the availability from the Yeast Genetics Stock Center at the University of California at Berkeley of a set of auxo trophic strains designed to permit mapping of most unknown genes with a minimum number of crosses and tetrad analyses. The first section concludes with the description of methods for hybridization of yeasts by protoplast fusion, which has been described as the poor man's system for genetic engineering.