Random amplified polymorphic DNA (RAPD) markers were used as input for an analysis of molecular variance (AMOVA), homogeneity of molecular variance analysis (HOMOVA), and cluster analysis to describe the population genetic structure ofIliamna corei, a federally endangered plant located only in Virginia, andI. remota, a rare plant in Virginia, Indiana, and Illinois. The analysis was performed to help clarify the taxonomic relationship between the two closely related species. We analysed four clones in the only known population ofI. corei, breeding stock derived from seeds originating from the population site, and threeI. remotapopulations in Virginia. Eighty-five percent of screened primers revealed DNA polymorphisms inIliamna. Ninety-nine informative markers were generated using seven primers. No significant statistical differences (atP = 0·05) in RAPD variation was found between species (24% of variance) using the AMOVA procedure. However, within species/among populations (31% of the variance) and within populations (45% of the variance) there were significant differences (P < 0·002). An unweighted paired group method using arithmetic averages (UPGMA) cluster analysis showed the federally endangeredI. coreipopulation to be genetically distinct from the apparently recently introduced (in Virginia: ≈ 100 ybp)I. remota. The lack of significant differences from the AMOVA and the high number shared bands betweenI. coreiandI. remotasuggest thatI. coreimay be more appropriately classified as a subspecies ofI. remota.Iliamna coreiplants in the natural population were genetically similar to one another while theI. coreibreeding stock plants andI. remotaplants were genetically relatively diverse.