A randomly amplified polymorphic DNA (RAPD) technique was used to identify and determine the phylogenetic relationships of 37 hosta accessions representing the major subgenera, sections and groups in the genus Hosta. Results of this study show that RAPD markers were able to differentiate not only the main groups, whose plants shared many genetic traits, but also cultivars within a species. Some accessions were identified by a single primer while others had high intercross linkage and required many markers for their separation. The phylogenetic clustering showed that H. plantaginea, the only night-blooming species, and H. ventricosa, the only known natural tetraploid, are unique and should be classified separately. The four species in the subgenus Bryocles, section Lamellatae H. venusta, H. minor, H. capitata, and H. nakaiana have very low genetic similarity since they do not share many amplified fragments. The other accessions were classified into four main clusters; cluster 1: H. venusta, H. tardiva, H. pycnophylla, H. tsushimensis `Ogon', H. montana, H. tibae, H. montana f. macrophylla, H. kikutii `Kikutii', H. longissima `Longifolia', H. rectifolia `Rectifolia', H. takahashii and H.`Undulata'; cluster 2: H. laevigata, H. sieboldiana, H. pycnophylla × H. longipes f. latifolia, H. longipes `Urajiro' and H. ibukiensis; cluster 3: H. capitata, H. kikutii `Polyneuron', H. nigrescens, H. kikutii `Yakusimensis', H. pachyscapa, H. kikutii `Caput-Avis', H. longipes f. latifolia, H. hypoleuca, H. okamotoi, H. densa and H. takiensis; and cluster 4: H. aequinoctiiantha, H. rupifraga, H. `Amanuma', H. minor and H. kikutii `Densa'.