Bluetongue (BT) was first recognized and described in Southern Africa, and only later elsewhere. It is now known that the causative agent of BT [BT virus (BTV)] occurs throughout temperate and tropical regions of the world. Previous OIE symposia in 1984, 1991 and 2003 clarified the global distribution of BTV and its epidemiology, pathogenesis, and diagnosis. Since the 3rd symposium in 2003, however, there have been significant developments. Notably, BT has emerged in Northern Europe and novel BTV serotypes have appeared in other endemic areas raising substantial questions regarding the environmental and anthropogenic drivers of emergence of BTV, including the invasion and spread of laboratory propagated viruses. Additional BTV serotypes with novel properties have recently been identified in Europe and the Middle East. Recent studies also confirm the importance of the Culicoides vector as the essential overwintering reservoir of BTV in temperate regions such as California and not ruminant livestock, proving wrong the prevailing thesis circulated prior to the 1st symposium in 1984. The challenge for participants of this 4th symposium is to predict collectively what the future might hold in terms of emergence of BTV globally, and what strategies are likely to be most feasible, justified, and effective for its control.