We obtained anti-IgG Sepharose-an immunosorbent with sheep monospecific polyclonal antibodies against human IgG-for extracorporeal removal of human IgG. Appropriate conditions for effective usage of the immunosorbent were chosen. Binding capacity and selectivity of anti-IgG Sepharose were determined and compared with the corresponding properties of other sorbents for IgG apheresis; these properties appeared to be acceptable for immunoapheresis procedures. Methods for therapeutic application of anti-IgG Sepharose is expected to be effective when used in immunoapheresis procedures for treatment of autoimmune diseases and for preparation of patients for organ transplantation.