The cranberry cultivar `HcFarlin', selected from a natural bog in Massachusetts in 1874, has become the most widely grown cultivar in the Northwestern U.S.A. Washington state growers have noted variable productivity among `McFarlin' bogs. The determination of whether there is a genetic basis for the variability has been made difficult by a paucity of reliable morphological descriptors in cranberry. A random amplified polymorphic DNA (RAPD) analysis of 45 clones sampled from 12 WA `McFarlin' bogs identified 17 unique RAPD profiles. Cluster analysis identified 7 groups having various numbers of distinct, but related individuals. Eight clones were found to have RAPD profiles identical to the cultivar `Howes' indicating varietal misclassification had occurred in some bogs. One group of clones that originated from bogs classified as “Good” or “True” Mcfarlin' by growers had RAPD profiles similar to those of representatives from WI and MA `Mcfarlin' bogs. RAPD analysis has shown that `McFarlin' is represented by several genotypes, suggesting that the observed variability in production may have a genetic component.