Abstract: Toxoplasma gondii tachyzoite was crescent-shaped. The pellicle of the parasite consisted of two membranes. The anterior end contained the polar ring and conoid, the former being the thickened inner membrane and the latter a cylindrical organelle which was made up of about 10 filaments arranged in an oblique row. The subpelli-cular microtubules numbering 22 originated at the polar ring and extended to the posterior end. The rhoptries extended from the conoid and terminated anterior to the nucleus with a narrow dense neck and an enlarged posterior portion with a glandulat structure. The rhoptries perhaps had a secretory function and the conoid might be related to the invasion of the tachyzoite into the host cell.