This paper discusses new evidence of long-distance interaction networks in Island Southeast Asia obtained from geochemical analyses using SEM-EDXA and LA-ICPMS of 101 obsidian samples from 25 locations including seven obsidian sources and 19 archaeological sites. Given that there are obsidian sources distributed throughout much of Island Southeast Asia, the potential for obsidian studies to provide greater understanding of patterns of mobility and exchange in the Pre-Neolithic and Neolithic periods would seem to be considerable. This potential, however, remains largely unrealised as obsidian sourcing has hitherto only been carried out intermittently in Island Southeast Asia using PIXE-PIGME, XRF and other methods.