This paper reports the community prevalence of 20 life traumas and considers their individual relevance as risk factors for psychiatric disorder. Also presented is the first evidence on the mental health significance of cumulative adversity as indexed by a count of lifetime exposure to a wide array of potentially traumatic events. The question of the importance of considering such events within efforts to assess variations in life stress is also examined. Our results demonstrate clear relationships between many traumatic events and, especially, accumulated lifetime trauma experience and both psychological distress and psychiatric disorder. That these relationships persist with temporal priority controlled - and net of the effects of parental psychopathology - suggest the causal relevance of major lifetime events and the conclusion that they represent on important dimension of increased mental health risk. From these findings and from evidence for the significance of traumas in disorder recurrence, it is contended that failure to take account of such events has resulted in the systematic underestimation of the role of stress exposure in accounting for variations in emotional distress and disorder.