Aim: We report on the investigation and management of patients, who were admitted at the Department of Occupational Health, University of Vienna, with a potential diagnosis of “Chronic Fatigue Syndrome” (CFS). Aim of the study was to establish guidelines for the diagnostic management of those patients. Method: 67 patients with the potential diagnosis of CFS were investigated between October 1999 and December 2001 in collaboration with the psychiatric services. Results and conclusion: We observed that the potential diagnosis of CFS could be confirmed only in 20 patients (30 %). This was due to the lack of fulfilment of the basic-criteria for the diagnosis of CFS (n = 30) as well as due to the presence of psychiatric disorders that exclude the diagnosis of CFS (n = 24). Neurological conditions (n = 5), organic conditions (n = 4) and adipositas (n = 1) which exclude the diagnosis of CFS were rarely present. Those 20 patients who fulfilled the diagnostic criteria of CFS often suffered from other psychiatric disorders (n = 45). This fact may imply an etiological association.