Nine strains of Pythium insidiosum the etiologic agent of pythiosis, were inoculated on 2% water agar plus grass blades and then incubated one day at 25 degrees C, 35 degrees C and 37 degrees C. Sporangium and secondary biflagellate-type zoosporas from the parasitized grass blades were noticed in induction medium after one hour of incubation at 35 degrees C and 37 degrees C. The number of sporangia and zoospores were lower at 25 degrees C, than 35 degrees C and 37 degrees C. Increasing the days of incubation of the parasitized grass blades resulted in the increase in the time of incubation in the induction medium. Corn meal agar, Schmitthenner medium and Sabouraud dextrose agar were also tested but the sporangium and zoosporas were always observed after five hours of incubation in induction medium.