The objective of this study was to evaluate the degree of RAPD marker variability between and within commercially productive market classes representative of the Andean and Middle American gene pools of common bean (Phaseolus vulgaris L.). Six sets of near-isogenic lines were screened with oligonucleotide primers in the polymerase chain reaction-based RAPD assay. Simultaneous analyses with at least three sets of lines enabled us to score RAPD markers between the two major gene pools, races within the same gene pool, and different genotypes of the same race (within race). A “three-tiered” pattern of polymorphism was observed: between gene pools> between races> within races. The overall level of polymorphism between the Andean and Middle American gene pools was 83.4%. The overall level of polymorphism between races within the same gene pool was similar for Andean races (60.4%) and Middle American races (61.7%). The level of polymorphism between related commercial navy bean lines was 39.2% and between related commercial snap bean lines was 53.6 %. The inherent simplicity and efficiency of RAPD analyses, coupled with the number of polymorphisms detectable between related commercial genotypes, should facilitate the construction of RAPD-based genetic linkage maps in the context of populations representative of most bean breeding programs.