Although there were few differences of flower colors among these groups, large number of individuals of Rhododendron kaempferi in southern Kyushu showed vivid red color whereas the almost all individuals in Tohoku district showed relatively somber red. It was unable to distinguish the individuals of northern Kyushu from those of southern Kyushu by anthocyanin constitutions of the petals. However, the latter individuals showed wider variations in the anthocyanin constitutions than the former. The unique anthocyanin was detected in the individuals in Tohoku district. From these findings, the anthocyanin constitutions of the petals were seemed to be the useful indices of regional variation of R. kaempferi distributing in Japan.