The dose-effect relationships of cumulative trauma to the psychiatric symptoms of major depression and post-traumatic stress disorder (PTSD) in a community study of Cambodian survivors of mass violence were evaluated. In 1990, a survey of 1000 households was conducted in a Thai refugee camp (Site 2) using a multi-stage random sampling design. Trauma history and psychiatric symptoms were assessed for two time periods. Analysis used linear dose-response regression modelling. 993 Cambodian adults reported a mean of 14 Pol Pot era trauma events and 1.3 trauma events during the past year. Symptom categories of depression, PTSD, dissociative and culturally dependent symptoms exhibited strong dose-effect responses with the exception of avoidance. All symptom categories, except avoidant symptoms, were highly correlated. Cumulative trauma continued to affect psychiatric symptom levels a decade after the original trauma events. The diagnostic validity of PTSD criteria, with the notable exception of avoidance, was supported. Inclusion of dissociative and culturally dependent symptoms increased the cultural sensitivity of PTSD.