BACKGROUND: There are concerns regarding the validity of combat exposure reports of veterans seeking treatment for combat-related post-traumatic stress disorder (PTSD) within US Veterans Affairs Medical Centers. AIMS: To verify combat exposure history for a relevant sample through objective historical data. METHOD: Archival records were reviewed from the US National Military Personnel Records Center for 100 consecutive veterans reporting Vietnam combat in a Veterans Affairs PTSD clinic. Cross-sectional clinical assessment and 12-month service use data were also examined. RESULTS: Although 93% had documentation of Vietnam war-zone service, only 41% of the total sample had objective evidence of combat exposure documented in their military record. There was virtually no difference between the Vietnam 'combat' and 'no combat' groups on relevant clinical variables. CONCLUSIONS: A significant number of treatment-seeking Veterans Affairs patients may misrepresent their combat involvement in Vietnam. There are implications for the integrity of the PTSD database and the Veterans Affairs healthcare system.