In recent years, the Wharton Risk Management and Decision Processes Center of the University of Pennsylvania has worked under a cooperative agreement with EPA to carry out a program of basic and applied research into chemical facility risk management. This report describes the major findings from all of the accident epidemiology studies conducted under the EPA-Wharton cooperative agreement. For example, during a decade-long period characterized by increasing economic activity and increasing hazard level at RMP-covered facilities, there has been a decline in the frequency of accidents reported by the approximately 10,000 facilities that have been continuously covered by the rule since its inception. Other research findings include a decline in toxic worst-case scenario vulnerable zones and the presence of a 'Texas City effect' in the statistical analysis of accident severity. Accidents with the largest reported consequences (such as the March 2005 explosion at the BP America refinery in Texas City, TX) had a very significant influence on the mean severity of all reported accidents. This finding highlights the importance of preventing low-probability, high-consequence accidents. The study concludes with a discussion of its limitations and suggestions for future research.