The present study deals with effects of the air temperature, and the type of medium on the growth and form morfological structures of six Seimatosporium hypericinum isolates tested. St Jonh's Wort extract agar, St Jonh's Wort plant agar and PDA, oatmeal agar has been recognized as most useful for growth and sporulation of S. hypericinum. Mineral agar, appeared the least useful for growth and form acervuli and conidia. S. hypericinum can develop in a wide range of temperature, but the optimum one for the growth and sporulation of the fungus vary between 20°C and 28°C.