Blotter yeast samples, liquid yeast samples, unfinished beer samples, unpasteurized beer samples, and some miscellaneous samples were tested for the presence of wild yeasts. By the combined use of lysine medium and LWYM, varying numbers of wild yeast contaminants, including wildSaccharomycesandnon-Saccharomycesspecies, were detected. The levels of wild yeast contamination in some samples were very high at such levels, spoilage was quite possible. It is suggested that wild yeast contamination problems in the brewery should not be ignored and that the detection of wild yeasts should be emphasized in the brewery quality control program.