Toxoplasma gondii is an obligate intracellular protozoan that infects a variety of vertebrate host including man. In immunocompetent host, symptoms are mild and non-specific, thus pathological information of acute toxoplasmosis in man is rare, Toxoplasmosis as a life-threatening disease in AIDS patients results form reactivation of previously quiescent infection. The presently available evidence suggests that host tissue pathology associated with T. gondii infection may play an important role in latent infection and reactivation process. We, therefore, studied the pathology of acute toxoplasma in experimental mice inoculated with 5x105 RH strain of Toxoplasma gondii. Light and electron microscopic pathological features found in their liver, spleen, pancancreas and brain of those mice studied, could be applied in man for further understanding of the pathogenesis of Toxoplasma reaction.