Résumé : Introduction: Non-alcoholic Fatty Liver Disease (NAFLD) is increasingly recognised as a source of liver related morbidity and mortality. Hard data on epidemiology and natural history are scarce. Aim: To study demographic and metabolic characteristics of the NAFLD patients seen by Belgian hepatologists. Methods: Belgian hepatologists filled in a questionnaire for every newly diagnosed NAFLD patient between January 1st and December 31st 2004. Liver biopsy was advised if ALT > 1.5 × ULN and if 3/5 of the criteria for the metabolic syndrome (MS) (ATPIII) were present, but was not mandatory. Biopsy was scored using the Brunt classification. Results: 230 patients were prospectively included in 9 centres; 54% were males; mean age was 49.4 ± 13.9 y; mean BMI was 30.6 ± 4.6 kg/m2. The MS was present in 53%. In 16% formerly undiagnosed diabetes was discovered. 51% had a liver biopsy: 25% met the criteria, 26% did not. Grading did not differ between patients with or without MS. Staging was significantly more severe in patients with MS (2.43 ± 1.25 vs. 1.73 ± 1.18, p < 0.001). A subgroup of patients with GGT > 5 × ULN were significantly older (55.9 vs. 47.64 y, p = 0.02), more frequently diabetic (53% vs. 23%, p = 0.01) and had more advanced fibrosis (3.42 vs. 1.08, p = 0.008). ALT levels were variable. Conclusions: The MS is highly prevalent in Belgian NAFLD patients and is associated with more severe disease. Mild to moderate fibrosis is frequent, and the proposed criteria for liver biopsy are not accurate in selecting these patients. Patients with elevated GGT constitute a subgroup with more advanced disease.