Recent survey efforts carried out in the Danau Sentarum National Park suggest that the site comprises faunal biodiversity of a bioregional and global importance. Site faunal inventory has yielded 240 confirmed fish species, or 71 per cent of Boreno's freshwater fish fauna; not including nineteen potentially new and endemic species awaiting confirmation. This suggest that the site is the most diverse in Indonesia with respect to fish and is also one of the world's most biodiverse lake systems. There are regionally significant listings of 237 confirmed bird species, and a tentative listing of 143 mammal species and all this provides ample justification for the initiation of immediate habitat and faunal community conservation effort on the site. However, there is not yet enough ecological detail to initiate firmer 'species-focused' conservation programmes. This data gap and the need for further ecological and taxonomic research is reaching crisis point as the risk of site and regional species extinction mounts in the face of accelerating habitat destruction and uncontrolled harvest and trade impacts. The introduction to the problem is followed by four detailed appendices of the fish species, the reptiles, the birds, and the mammals to be found on site.