ABSTRACT. Munhoz A.D., Bandarra M.B., Vasconcelos R.O., Mineo T.W.P. & Machado R.Z. Use of embryonated egg membranes in the standardization of immunohistochemistry protocols for Toxoplasma gondii. [Utilização de membranas de ovos embrionados na padronização de protocolos de imunohistoquímica de Toxoplasma gondii.] Revista Brasileira de Medicina Veterinária 36(4):401-404, 2014. Departamento de Patologia Animal, Universidade Estadual Julio Mesquita Filho, Unesp/Jaboticabal, Rod. Paulo Castellane s/n, Jaboticabal, São Paulo, SP 14884-900, Brazil. E-mail: email@example.com The chorioallantoic membranes of embryonated eggs can be used in the standardization of immunohistochemistry (IHC) protocols to detect Toxoplasma gondii antigens. On the 10th day of embryogenesis, four groups received, respectively, 1x104 , 1x105 , 5x105 and 1x106 T. gondii tachyzoites (RH strain)/ 100 µL, and a control group received PBS (pH 7.2). Three forms of heat induced antigen retrieval were employed (double boiler, electric cooker and Pascal pressure chamber) in the IHC. A diffuse distribution of the parasite was observed in the IHC of all infected groups. The results of the various antigen retrievals were similar for all slides, with no differences demonstrated as to the retrieval forms applied. The use of membranes as positive controls in IHC reactions for T. gondii provides parasite-rich material that is easy to prepare and shows quick results, making it a useful tool in the standardization of protocols for this purpose.