Amami Oshima, a World Natural Heritage candidate, is an island in the south of Japan, lying at the northern margin of subtropical climate and immediately in the south of Watase Line, a major biogeographic boundary between temperate and tropical biota. Here I report the structure and composition of three new 1-ha plots of evergreen broad-leaved forest (EBLF), established at different altitudes (200, 400 and 600 m) on Amami Oshima (maximum elevation 694 m), and compared them with the existing 1-ha plot (330 m). Although these four (three new and one existing) plots were located in the most developed stands in the National Forest (so-called ‘virgin forest’ with no documented record of logging), all the four plots seem to be at younger stages of succession than old-growth EBLF plots in mainland Japan (including Yakushima). Altitude, topography and successional status seem to account for the structural and compositional variations among the four 1-ha plots. The relatively young successional status (including high dominance of Castanopsis sieboldii) of the forest should be due to either or both of human and natural (wind) disturbances, and further study focusing on forest dynamics is necessary to resolve this contention.