Menziesia goyozanensis, a Japanese kindof fool's huckleberry, is a shrub speciesendemic only to Mt. Goyo in northern Japan.This species is listed as `criticallyendangered' in the Red Data Book of wild plantsin Japan, and only a single population has yetbeen discovered. The allozyme diversity andRAPD variation of Menziesia pentandrawere eight- and threefold greater than those ofM. goyozanensis, respectively, althoughwe examined only five populations representinga part of the distribution of M.pentandra. Because the environment surroundingthe population of M. goyoznaensis seemsto be stable at present, it is not necessary toplan an urgent ecological conservation practicefor the species. However, considering that thehabitat of M. goyozanensis is very smalland large vegetative disturbances occasionallyoccur in cool temperate forests, in which thespecies dwells, ex situ conservation isessential.