Three taxa in Rubus (Rosaceae): R. parvifolius, R. coreanus, and R. × hiraseanus, a presumed spontaneous hybrid between the former two described by Makino in 1902, were investigated cytologically. The somatic chromosome numbers were found to be: 2n=14 for R. parvifolius and R. coreanus and 2n=21 for R. × hiraseanus. The chromosome number of the latter was determined for the first time. The karyological features of R. parvifolius and R. coreanus were similar, and further gross similarity was also observed in the chromosomes of R. × hiraseanus, although the size of the satellites and ploidy level differed. The chromosome configurations found in the PMCs of R. × hiraseanus displayed frequent trivalent formation, indicating that R. × hiraseanus may comprise three homologous sets of chromosomes. This study indicated the possibility of a close relationships, but failed in elucidating an origin for R. × hiraseanus.