This report presents the initial results of a mental health survey of 351 tribal and non-tribal Mount Pinatubo disaster victims 6 years after they were displaced following the volcanic eruption in the Philippines on June 12, 1991. Mental illness prevalence rates in both Filipino ethnic groups were comparable to those found in a U.S. study using the same assessment instrument. Post-traumatic stress disorder (PTSD; 27.6%) and major depression (14.0%) were the two most frequent diagnoses. Diagnostic test-retest interviewer agreement was good for probable alcohol abuse (κ = .65, agreement = 97%) and any mood disorder (κ = .53, agreement = 91%) but was reduced for any anxiety disorder (κ = .15, agreement = 81%) and separately evaluated PTSD (κ = .18, agreement = 69%). Diagnostic test-retest agreement was good among typical Filipinos (mean κ = .66, mean agreement = 93%) but was reduced among tribal aborigines (mean = .30, mean agreement = 86%). Internal consistency of the PTSD rating scale was high within and across both ethnic groups, including total scale (α = .91) and DSM-IV Criteria B, C, and D sub-scales (α = .80, 81, and .78, respectively). With the exception of probable alcohol abuse, construct and criterion validity was demonstrated among both tribal and non-tribal Filipinos for all classes of psychiatric disorders by comparing diagnostic results with respondents' views of their physical and mental health and level of functional impairment. Overall, DSM-IV mood, anxiety, alcohol use, and PTSDs with adequate reliability and construct and criterion validity were made in this culturally diverse, non-Western, disaster victim population. However, test-retest diagnostic agreement was reduced for anxiety disorders and among aboriginal respondents, and validity was not demonstrated for probable alcohol abuse.