A 60 kD SS-A/Ro recombinant protein was expressed in E. coli cells and purified by the centrifugation procedure. Since the substrate contained a substantial amount of bacterial proteins it was not sufficient for ELISA. Therefore the material obtained by centrifugation was resolved on SDS-gel and the 60 kD region was excised and electro-eluted. Two hundred and nine sera from normal donors and patients with rheumatic diseases were analyzed by ELISA using the purified recombinant 60 kD SS-A/Ro protein. A comparison with Ouchterlony and Western blot revealed that ELISA proved to be a sensitive and specific method, which could discriminate between anti 60 kD antibodies and other autoantibodies. The present study showed that recombinant 60 kD may provide a purified source of antigen for ELISA while this method may serve as a useful tool for screening and evaluation of anti 60 kD antibodies and their relevance to clinical manifestations.