The distribution ofPhyllostachys pubescens, introduced to Japan from China in 1736, has been expanding. The expansion was studied in Tanabe Town, Kyoto Pref., Central Japan. Long term expansion was traced using a topographic map, a land-use map and aerial photographs. Within the research region (21.35 km2), the number and total area of bamboo sites increased from 24 and 0.16 km2in 1953 to 174 and 3.04 km2in 1985. By contrast, the total area of tree sites decreased from 12.2 km2in 1953 to 8.5 km2in 1985. The average area of bamboo sites also increased from 0.67 ha in 1953 to 1.75 ha in 1985. The average rates of the current expansion, measured by censusing current and old culms in the front of 10 unmanaged bamboo sites, were 2.1 m yr-1. Stand structure was detailed in a transitional area from a pure stand ofP. pubescensto a mixed broadleaved forest. Stand structure was simpler in the area dominated byP. pubescens.Culms off!pubescenswere larger in the pure stand, and variations in DBH and height were smaller for the bamboo than for the trees in each sample site.P. pubescenshad a greater average crown length and higher canopy position. These traits allowP. pubescensto invade adjacent forests, form a uniform monolayer of foliage, and dominate competing vegetation. There was no evidence of seedling regeneration under the bamboo. More than two-thirds of the Japanese forest is secondary growth or young plantations of conifers, and in most of these, canopy height is lower than that ofP. pubescens.The continuous area increment in bamboo from 1953 to 1985, positive current expansion rate in the front of unmanaged bamboo stands and the advantageous stand structure of bamboo suggest that the range expansion ofP. pubescensin the secondary forest will continue in the future.