The Toxoplasma gondii IgG test is quantitative and qualitative immunoassays for the detection of human antibodies in serum or plasma directed against Toxoplasma gondii. The Toxoplasma gondii IgG test allows for the determination of immune status as well as for the detection of intrathecally synthesized antibodies for CSF diagnostics and, by using the corresponding avidity reagent, of IgG antibody avidity determination in order to differentiate acute from past infections.