Data Mining procedures were used to analyze responses of 173 missionaries surveyed about the nature and impact of traumatic stress (TS) they may have experienced while on the field. TS was almost universal, with the most frequent types involving system failure or personal crisis; there was also a high incidence of permanent negative change in those reporting TS, and over a third of these reported continuing symptoms almost a decade post-incident. Non-catastrophic stressors and stressors involving System Failure (particularly those with peer-System Failure) had higher TS impact. Severity, as seen in Total Impact and Total Number of Symptoms, was related to permanent negative change, as was age, with younger missionaries (possibly a generational rather than age or experience issue) being more vulnerable. Both destructive and salutogenic change were associated with TS, but no predictive variables were found for the latter.