Technical Abstract: Food and beverage spoilage yeasts often show some degree of substrate specialization. Species of Zygosaccharomyces and related genera (i.e., Lachancea, Torulaspora and Zygotorulaspora) are usually the yeasts that colonize and spoil high sugar and high salt products such as fruit juices and their concentrates, dried fruit, honey, jams and preserves, soft candy, salad dressings, soy sauce and sugar syrups (Kurtzman, 1998a; 1998b; Barnett et al., 2000; James and Stratford, 2003). Growth of these species can be slow with an apparently good product leaving the manufacturer only to become spoiled after several weeks or months on the grocery store shelf. The most obvious problem seen for spoiled products is gas buildup in the container. The gas, which is carbon dioxide, results from slow fermentation of sugars in the products. The carbon dioxide buildup may be sufficient to cause the distortion or even explosion of either the product, e.g., fondant-filled chocolate cream eggs, or the product packaging. In the case of glass containers, these can sometimes shatter resulting in injury (Grinbaum et al., 1994). Other types of spoilage caused by these species include the generation of taints, odors and off-flavors, and the development of hazes due to substantive yeast growth. Yeast spoilage ordinarily does not lead to human infections or formation of toxic products, but changes in product composition might result in concurrent growth by pathogens or microorganisms that produce toxins. In this chapter, methods for isolation, quantitation, identification and control of spoilage yeasts will be presented. Newly developed molecular methods for species identification will be discussed along with traditional methods based on phenotypic characterization.