OBJECTIVE: Most of the data on psychological outcome and the mental health treatment available following natural disasters originate from the indigenous population of the region destroyed. Examining tourists returning from the area affected by the 2004 tsunami presents an opportunity of studying the impact of natural disasters on psychological outcome and mental health treatment in their countries of origin. The aim of the present study was to extend the current knowledge on psychiatric morbidity and potential positive outcomes, as well as subsequent mental health treatment following a natural disaster, based on the results from a sample of home-coming Swiss tourists. METHOD: Tourists who had been potentially affected by the 2004 tsunami were assessed using the Post-traumatic Diagnostic Scale, the Hospital Anxiety and Depression Scale, and the Post-traumatic Growth Inventory. Outcome variables were related to the degree of tsunami exposure. In addition, mental health treatment before and after the tsunami was assessed. RESULTS: Of the 342 respondents, 55 (16.8%) fulfilled the criteria of post-traumatic stress disorder (PTSD). Evidence of anxiety or depressive disorder was found in 17.8% and 8.0%, respectively. The tsunami victims who had been directly affected showed significantly more symptoms of anxiety, depression and PTSD, as well as post-traumatic personal growth, than tourists who were indirectly affected or unaffected. A total of 12.3% of untreated respondents fulfilled the criteria for PTSD and 38% of respondents who had received psychiatric treatment were still fulfilling PTSD criteria 2(1/2) years after the tsunami. CONCLUSION: A marked percentage of respondents reported symptoms of PTSD but they remained untreated or were treated insufficiently. We recommend that tourists returning from regions affected by natural disasters be informed about PTSD and that careful screening be given to those found to be at risk of PTSD. An open-door policy of mental health services is particularly needed for tourists returning home who have been affected by large-scale disasters.