Chronic Fatigue Syndrome (CFS) is a complex and multifactorial disease. Stressful situations experienced could be related to the presentation of the disease. Few studies have determined which factors could trigger CFS. The main objective of this study was to explore the stressful situations which can be associated with CFS presentation. METHODS: Retrospective observational case-control study with CFS diagnosed patients according to the Fukuda's criteria. Controls were matched to cases by sex, age and educational level with a 1:1 ratio. Participants aged between 18 and 75 years from the province of Lleida. Information was obtained through personal questionnaires. The measure of association was the odds ratio. RESULTS: In total, 77 cases and 77 controls were included. Association found between stressful life events and presentation of disease were pregnancy ORa=31.7 (CI95%:2.2-456.7), spousal abuse ORa= 10.2 (CI95%:1.2-88.4) and mobbing ORa=6.9 (CI95%:1.3-36.9), eating disorders=7.5 (CI95%:1.3-42.1), car accident ORa=5.5 (CI95%:1.7-17 9), economic problems ORa=5.1 (CI95%:2.1-12.6) and changes in sleep habits ORa=2.8 (CI95%:1.1-7.5). CONCLUSIONS: Stressful life events as pregnancy, spousal abuse, mobbing, eating disorders, car accident, economic problems and changes in sleep habits felt by those affected must be taken into consideration when compiling background information related to the onset of Chronic Fatigue Syndrome. Adequate identification of these stressful life events in risk people could contribute to early diagnosis of Chronic Fatigue Syndrome.