Genetic differentiation was investigated among 54 Indonesian species of Dipterocarpaceae, a dominant tree family in Asian tropical rainforests, using amplified fragment length polymorphism markers. The tree developed from the resultant unweighted pair group method using arithmetic averages clearly separated all investigated dipterocarps into two major groups that corresponded to tribe Dipterocarpeae and tribe Shoreae, respectively. These results are in accordance with the topology of molecular phylogenetic trees derived from PCR-restriction fragment length polymorphism analysis of chloroplast DNA and generally support the traditional taxonomic assessments. The possibility of interspecific hybridization is also discussed.