Proteins from Toxoplasma gondii were separated by SDS-PAGE and then transferred to a nitrocellulose membrane. Antigenic components were then detected by human sera with previously known Toxoplasma antibody levels. Peroxidase-conjugated anti-human immunoglobulins were used for the separated identification of IgG and IgM reactive proteins. IgGand IgM Toxoplasma antibodies showed very different patterns of reaction with antigenic components. IgG Toxoplasma antibodies reacted with numerous antigens of molecular weight ranging from 13000-98000 hDa while IgM Toxoplasma antibodies detected only a few polypeptides with molecular weight ranging from 19000-88000 kDa