Toxoplasmosis is a world-wide spread parasitosis. The disease potentially highly affects two groups of patients: foetus and immunosuppressed patients. The determination of diagnosis and therapy on the basis of a single serum examination is very important; possible on the basis of a single serum sample. In most cases, it is possible to differentiate between recent and latent infections using a combination of suitable methods, which permit us to confirm particular antibody classes. In the presented paper the authors suggest diagnostic procedures for 4 groups of patients: pregnant, neonates with suspected congenital toxoplasmosis, immunodeficient patients and immunocompetent patients. The diagnostic methods consist of a combination of basic and supplemented diagnostic methods. Each patient's serum should be tested by basic tests which include the detection of total antibodies with CFT or IFT and specific classes of IgM and IgG antibodies by ELISA. The potential activity of toxoplasma infection can be determined by supplementary methods of e.g. IgG avidity antibodies, establishment of IgA antibodies, western blotting method and monitoring of antibodies production. For each situation the authors present interpretations of suspected cases including proposals for clinicians. These procedures are suggested for practical use in laboratories of various diagnostic levels in order to help to the diagnostic procedures in a particular situation as well as for clinical evaluation of established results. (Fig. 4, Ref. 65).