Autoantibodies against nuclear pore membrane glycoprotein gp210 have been identified in between 10% and 25% of patients with primary biliary cirrhosis (PBC). These antibodies may be useful in diagnosing PBC and in identifying subgroups of patients. Because previous detection procedures relied on the need to purify hydrophobic proteins and perform immunoblotting, the aim of the present study was to develop a simple assay to detect gp210 autoantibodies. A recombinant polypeptide containing glutathione-S-transferase (GST) fused to the region of gp210 that contains its predominant autoepitope(s) was expressed in bacteria. This fusion protein was purified by glutathione-Sepharose chromatography and used in an enzyme-linked immunosorbent assay (ELISA). The ELISA was reproducible in detecting gp210 autoantibodies in serum samples from patients with PBC. Compared with immunoblotting, the ELISA was 93% sensitive and 96% specific for the detection of gp210 autoantibodies. In conclusion, autoantibodies against gp210 can be easily and reliably detected in patients with PBC by an ELISA that uses a purified recombinant polypeptide. (HEPATOLOGY 1995;21:495–500.)