['We sought to determine whether features of metabolic syndrome (MS) and histologic features of nonalcoholic steatohepatitis (NASH) are associated with increased fibrosis in patients with primary biliary cirrhosis (PBC).', 'PBC is a chronic, progressive cholestatic disease. MS is strongly associated with NASH and fibrosis progression in some liver diseases.', 'Patients with PBC seen consecutively at the University of Miami between 1985 and 2008 who had antimitochondrial antibody positivity and a liver biopsy performed at this center at the time of diagnosis were identified. Demographics, clinical features, and biochemical parameters were collected. All liver biopsies were reviewed by a single blinded pathologist for features of NASH, PBC, and fibrosis. The impact of NASH and features of MS on liver biopsy findings were analyzed.', 'Forty-nine patients [median age 51 (34 to 78) years, 98% females] were enrolled. Higher degree of steatosis, severe inflammatory grade, and severe biliary duct damage were each associated with advanced fibrosis (P<0.0001). Regarding MS, only overweight status [body mass index (BMI) ≥ 25] was associated with nonalcoholic fatty liver activity score (NAS) ≥ 5 (P<0.0001), biliary duct damage (P<0.0001), and advanced fibrosis (71% vs. 32%, P=0.007). Patients with NAS ≥ 5 had more severe fibrosis (14/15, 96% vs. 11/34, 44%; P=0.0001) and more severe biliary duct damage (13/15, 87% vs. 3/34, 9%; P=<0.0001).'] Is primary biliary cirrhosis more severe in overweight patients?