The Phaff Yeast Culture Collection at the University of California Davis is one of the largest and most diverse collections of wild yeasts in the world, with over 7,000 strains. The collection is a living legacy, meticulously collected over 50 years by eminent yeast microbiologist Herman Phaff (1913-2001) with isolates from foods and beverages, decaying plant material and associated insects. Roughly half of the known yeast species are represented. Over 80% of the strains are not available from any other source, which differentiates this collection from most other public repositories. The collection offers several services. Hundreds of yeast strains can be screened for novel properties such as tolerance of stresses associated with industrial fermentations, or production of high-value metabolites. A library of over 1,000 genomic DNA preps can be screened by PCR. Strains are distributed to academia and industry for research applications such as biofuels, industrial enzymes, food-grade pigments, and taxonomy. Collection staff select promising strains for specific applications utilizing a database of over 50 years of unpublished characterization data including over 80 physiological tests, such as utilization of xylose and expression of protease and lipase activities. Research projects include investigations of xylose utilization, production of higher alcohols for biofuels, and yeast-based lures for agricultural insect pests. Recent discoveries include yeasts that produce lycopene, isobutanol, or isoamyl alcohol, and yeasts that tolerate low pH or high alcohol concentrations. More information, including a strain catalog, can be found online at www.phaffcollection.org.