Toxoplasma gondii is the causative protozoan of toxoplasmosis which has a worldwide distribution among humans and warm-blooded animals. The diagnosis generally depends on serologic tests but the persistently high Immunoglobulin M (IgM) or low IgG avidity complicate diagnosis. It is essential to identify acute-stage-specific antigen to use in a single test for the definitive diagnosis of the acute disease, especially in pregnant women and immunocompromised individuals. In this study, we investigated the recognition of proteins of lysate antigen (LA) and excretory-secretory antigen (ESA) fractions of the virulent RH strain of T. gondii by the sera of patients who had recent or past infections and the sera of experimentally infected mice. As a result, no specific bands for discrimination of recent infection from the past one could be detected in our study but the results confirmed that proteins of approximately 20, 30 and 40 kDa were among the major targets for IgG responses during acute and chronic infection with T. gondii in humans.