<qa>  What is the unique opportunity to evaluate the effectiveness of ALS interventions on the outcomes of criticallyImportance: This proposed study has a unique opportunity to evaluate the effectiveness of ALS interventions on the outcomes of critically ill and injured patients. Never again may there be such an opportunity to conduct a controlled evaluation of the impact of an ALS program in such a large population. The results of this study will be very important to health care planners in Canada and throughout the world. 