To date, liver biopsy is the most sensitive test for detecting and staging NAFLD, and is the only reliable method for differentiating between NASH and simple steatosis. However, the procedure of obtaining a liver biopsy is invasive and associated with patient discomfort, significant complications and high costs. In addition, liver biopsy is prone to sampling error and inter- and intra-observer variability, due to the small size of liver biopsy samples. This method is therefore not suitable for screening large numbers of subjects at risk, or for follow-up of patients with NASH over time. Hence, only subjects at high risk (usually based upon elevated aminotransferase levels, which is not specific for the presence of NASH) are biopsied, leading to an underestimation of NASH prevalence and undertreatment. Further insight into disease mechanisms and risk factors for NAFLD and in particular NASH is warranted, to enable early diagnosis, adequate therapy and preventive measures to improve health status of these individuals. Accurate and less invasive methods to evaluate NASH, and NAFLD, are urgently needed.