There is marked overlap between non-alcoholic fatty liver disease (steatosis and steatohepatitis) and the metabolic syndrome phenotype. A comprehensive metabolic screening of 73 Chinese patients with biopsy-proven NAFLD and no history of diabetes revealed that 33% had undiagnosed diabetes and 29% impaired glucose tolerance according to the 2006 American Diabetes Association criteria. Among patients with 2-h plasma glucose >7.8 mmol/l, 47% had normal fasting glucose (<5.6 mmol/l), impaired glucose tolerance being more common in patients with non-alcoholic steatohepatitis than in those with simple hepatic steatosis, and 2-h plasma glucose correlating with fibrosis stage. Although fasting glucose and low HDL-cholesterol were independent predictors of diabetes, 20.8% of diabetes cases would have been missed if oral glucose tolerance tests were only carried out in non-alcoholic fatty liver disease patients with impaired fasting glucose. Therefore, postchallenge hyperglycaemia in this patient population cannot be accurately predicted by any fasting glucose cut-off.