Simple-sequence repeats (SSRs) are efficient and informative DNA markers with great potential for germplasm characterization. When used to characterize large arrays of accessions, such as the core subset of the USDA/ARS Malus collection, SSRs may be more effective than other approaches, such as restriction fragment length polymorphism (RFLP) and random amplified polymorphic DNA (RAPD). For example, SSRs can be PCR-amplified and fluorescence-based detected; they also appear to be abundantly disbursed throughout plant genomes and yield abundant polymorphisms in most taxa studied. We are conducting an extensive screening of a size-fractionated library of Malus ×domestica cv. Golden Delicious to identify and characterize selected SSR loci. We are applying genetic information revealed by SSR loci in combination with passport and horticultural data to better comprehend genetic identity and relatedness in Malus germplasm collections and help develop the Malus core subset. Ultimately, application of molecular marker data will permit improved conservation and use of genetic resources.