Reasoning under uncertainty is  pervasive in all areas of Artificial Intelligence. The ECSQARU Conferences are, every two years, a major forum for advances  in  the  theory  and  practice of reasoning under uncertainty. Contributions come both from researchers interested in  advancing  the  technology  and  from practitioners who are using uncertainty techniques in applications. The previous Ecsqaru conferences that have been held in Marseille (1991), Granada (1993), Fribourg (1995),  Bonn (1997), and London (1999).