Ultrathin sections of tissue cysts isolated from the brain of Toxoplasma gondii
infected mice were submitted to two different methodologies derived from the periodic acid - Schiff's reagent (PAS) technique. The use of osmium tetroxide vapor as a developing agent of the aldehyde oxidation to reveal polysaccharides with periodic acid resulted in positive reaction in amylopectin granules in bradyzoites, as well as in the wall and matrix of the cysts, with excellent increment of the ultrastructural morphology. This technique can be used for study of T. gondii
-host cell intracellular cycle, the differentiation tachyzoite-bradyzoite, and also for the formation of cysts into the host cells.