The ARS pea (Pisum) germplasm collection contains 3918 accessions catalogued by the USDA over the past century. Establishing genetic relationships among these accessions and developing a marker-saturated refined collection that is reflective of the broad genetic diversity available within the overall collection will facilitate research by those interested in utilizing the collection for crop improvement and association mapping. The first Pisum core collection (selection based on geographical origin and flower color) contained 504 accessions (Simon and Hannan 1995). Extensive phenotypic data associated with yield components (McPhee and Muehlbauer 2001), mineral nutrient (Grusak et al 2003) and seed protein content (Coyne et al 2003a) were used to eliminate redundancy and further refine the core collection to 310 of the original 504 accessions (Coyne et al 2003b). The current research details the phylogenetic relationships among the refined core collection based on 26 phenotypic measurements, 35 RAPD and 20 microsatellites loci. Nei's genetic distance estimates were first obtained separately for the phenotypic (quantitative) and the molecular marker (qualitative) data using the SIMINT module SIMQUAL modules (NTSYpc), respectively. Separate dendrograms were generated from the Sequential, Agglomerative, Hierarchical, and Nested (SAHN) clustering method using unweighted pair-group method, arithmetic average (UPGMA) (Sneath and Sokal, 1973; Rohlf, 2000) and a consensus dendogram was also constructed using the CONSENS module (NYSYpc).