Reports from North America and Northern Europe have suggested that antimitochondrial antibody (AMA) negative primary biliary cirrhosis (PBC) is a distinct chronic cholestatic liver disease with high prevalence of serum non-organ-specific autoantibodies other than AMA. To evaluate if such a peculiar serum immunoreactivity is associated with clinically relevant characteristics, we reviewed our experience with 297 Italian patients who have had a clinical and histological diagnosis of PBC and were regularly followed-up at our Center from June 1974 to June 1994. AMA-negative and AMA-positive patients were compared in terms of biochemical and clinical features, and clinical outcome of the disease. At presentation, 30 of 297 patients (10%) tested negative for AMA by indirect immunofluorescence. Six of them tested positive for antimitochondrial M2 antibodies (AMA-M2) by immunoblotting analysis, therefore, diagnosis of AMA-negative PBC was made in 24 patients (8%). At the initial visit, AMA-negative and AMA-positive patients were similar in terms of biochemical and clinical features. Antinuclear and anti-smooth-muscle antibodies (ANA and ASMA) were more frequently positive in the AMA-negative patients (71% vs. 31%, and 37% vs. 9%; both P = .0002). Incidence of complications of cirrhosis and development of liver failure resulting in death or referral for liver transplantation did not differ significantly between the two populations. In conclusion, data from this historical cohort study suggest that the distinct serological features of AMA-negative PBC are not associated with substantial differences in the clinical spectrum or course of the disease.