A rapid and systematic tandem LC-MS protocol is utilized to identify oligostilbenes in two Shorea species (Shorea leprosula and Shorea macrophylla; family Dipterocarpaceae). Analyses were performed by a newly developed dereplication system on a liquid chromatography-ion trap-mass spectrometry (LC-IT-MS) with electrospray ionization (ESI) interface. The combination of effective separation by an HPLC and multiple fragmentation steps for specific masses in MS enable fast and sensitive analysis of various degrees of oligostilbenes condensation.