NAFLD and alcoholic liver disease affect a substantial proportion of the population worldwide. Although presence and amount of steatosis can be determined with a good level of accuracy using noninvasive imaging techniques, currently, there is no available noninvasive tests to distinguish between simple steatosis from steatohepatitis or to stage fibrosis that had demonstrated to be simple, reproducible, and valid in patients who have NAFLD or alcoholic liver disease. Liver biopsy remains a useful tool to confirm the diagnosis and exclude other liver disease and remains the only investigation able to provide prognostic information by staging and grading these diseases. Noninvasive serum markers offer considerable promise in their ability to stage liver fibrosis. Routine liver tests may detect occult cirrhosis but are insensitive at predicting lesser stages of fibrosis. Several serum markers of collagen synthesis and degradation are not validated sufficiently and are not available in most medical centers to replace liver biopsy. These markers currently may assist in stratifying patients who are more likely to have advanced fibrosis and, therefore, may benefit from proceeding with liver biopsy. It is likely the more complex models, which include multiple serum markers, will be more accurate at predicting fibrosis. These currently have limited ability at predicting the full range of liver fibrosis, generally having the greatest diagnostic accuracy at predicting advanced fibrosis or absent fibrosis but not in-between. Measuring liver stiffness with different imaging techniques holds promise, but further carefully designed studies are necessary before they can be recommended in clinical practice.