Foresters generally accept without alarm the normally small but continuing losses caused by the indigenous agents of mortality in forest stands. When a stand suffers a sudden increase in the rate of mortality, however, attention is focused upon the subject and a host of questions and speculative answers arise. How much growth is nullified by mortality during a rotation? What are the causes of mortality and how important is each one? Is there any relationship between the cause of mortality and the age, density, composition, or other qualities of the stand? How much mortality might be salvaged under intensive management? These questions and others have been voiced many times by foresters working in the western white pine type. However, accurate quantitative information has been lacking and such questions have largely gone unanswered.