Collections containing microbes (often referred to as “culture collections”) and collections of seeds or clonal materials for higher plants (often referred to as “germplasm collections”) can provide abundant resources for plant pathologists, breeders, geneticists, and other plant science professionals. However, many such professionals (including graduate students, postdoctoral fellows, and technical staff) lack adequate guidance on locating, obtaining, and processing such materials. Regulatory procedures and considerations of biological security, ambiguities regarding intellectual property rights, lack of knowledge about collection databases, and other hurdles dissuade many professionals from effectively exploiting collection resources. The Collections and Germplasm Committee of the American Phytopathological Society, together with colleagues from international collections and the World Federation of Culture Collections, has assembled this guide summarizing the benefits and utilization of living collections for plant pathology. We show how to locate major and minor collections, obtain biological materials, and comply with regulatory and shipping requirements. We briefly discuss the relevance of intellectual property rights, the problem of endangered collections (especially those with invaluable and irreplaceable materials), and make specific recommendations for the support of living collections. Prior reviews of culture collections originated from diverse perspectives. Examples from an extensive literature are quality control and preservation (27,41, 47,54,68), taxonomy and research (13,26), organizations, legislation, and regulation (77), relevance to plant pathology and other disciplines (51,52,73), and genomics (50,68). Capsule histories of several culture collections, plus extensive lists of associated databases, are available (50). Public seed banks have been subjected to similar review. The USDA-Agricultural Research Service National Plant Germplasm System (NPGS) was the subject of detailed reporting, covering history (66,83), management (16), quality control and preservation (10,65,82), structure (1,16,86), personnel (86), information technology (53,67), conserved species (38,66), collecting of germplasm (58,84), and examples of associated research (86). For Canada, the locations and holdings of seed banks and clonal repositories were reviewed, and instructions were provided for online viewing and ordering of holdings (8). Earlier, multifaceted reviews (7,9) gave a worldwide perspective on plant germplasm. The fiscal health of collections has been the subject of repeated reviews (or perhaps more accurately, laments) and news items (2,11,73). Although we firmly acknowledge the importance of nonliving collections (museums and herbaria), we have chosen to restrict our discussion to collections of living materials. Readers wishing to learn more about herbaria and other nonliving collections are referred to other sources (37,46,87). Here, we concentrate on collections containing organisms that can be maintained in refrigerated conditions (as with many seeds or clonal stocks of higher plants) or grown in culture and then lyophilized or kept in cryogenic storage at ultra-low temperatures (as with many microorganisms). Some obligate parasites or symbionts are also kept in collections (e.g., plant viruses, vesicular-arbuscular mycorrhizal fungi and rusts), either in cryogenic storage or by maintaining them on their plant hosts.