Tree from 20 plots located on the eastern and northern slopes from the base to the summit of Hinidumkanda hill forest were enumerated and measured. Of the 3818 trees over 30cm d.b.h., 3770 were identified botanically. Vertical distribution, density and girth size distribution of the plants at the summit; b.a. per ha was similar for all 3 elevations. Floristic richness decreased by almost 50% with increasing altitude. Dominant species (based on density) in each of the strata were different for each elevation. There were 2 or more co-dominant species in the low and summit plots but only 1 species co-dominant in the middle elevation plots. Hinidumkanda has the highest percentage of endemic tree species (75%) and endemic tree individuals (80%) of all the aseasonal lowland rain forests sampled in Sri Lanka.