Nonalcoholic fatty liver disease (NAFLD) is prevalent in obese patients. We sought to determine the effects of bariatric surgery on the histological features of NAFLD. Two blinded pathologists graded liver biopsies done during bariatric procedures and subsequent operations in 160 patients using the Brunt classification. Data are mean ± SD. Interval between biopsies was 31 ± 26 months. Initial biopsies demonstrated steatosis 77 %, lobular inflammation 39 %, and chronic portal inflammation 56 %. Steatohepatitis was present in 27 %. Grade 2-3 fibrosis was present in 27 %, and cirrhosis was present in one patient. On post-bariatric biopsy, steatosis resolved in 75 %, lobular inflammation resolved in 75 %, chronic portal inflammation resolved in 49 %, and steatohepatitis resolved in 90 %. Fibrosis of any grade resolved in 53 % and improved in another 3 % of patients. Grade 2 fibrosis resolved in 58 %, improved in 3 %, and did not worsen in 11 %. Bridging fibrosis resolved in 29 %, improved in 29 %, and did not worsen in 29 %. Bariatric surgery is associated with resolution of steatosis or steatohepatitis in the majority of patients. More importantly, grade 2 or 3 (bridging) fibrosis is resolved or improved in 60 % of patients. Bariatric surgery should be considered as a treatment of NAFLD in severely obese patients.