The hybridoma technology was used to produce monoclonal antibodies to human ceruloplasmin. The antibodies were found to be related to Ig G1. Using these monoclonal antibodies for PAP-ELISA of ceruloplasmin, it was possible to determine 10(-11) M of the protein. Monoclonal antibodies coupled to CNBr-Sepharose were used for the rapid one-stage purification of ceruloplasmin from human placental serum. Ceruloplasmin obtained by this method contained no type 2 copper normally detected in protein preparations by conventional methods.