The use of Alternaria crassa (Saco.) Rands as a control agent of Datura stramonium L. has been studied in this work. A. crassa was isolated from infected seeds and leaves of D. stramonium ascetically on water agar (WA) at 25°C. Cultural studies were done to determine the best media, optimum temperature, light and pH conditions necessary for maximum growth and sporulation of the fungus. The fungus grew fast and sporulated best at 29°C, alternating light (8hr Darkness and at a pH of 6.8. Media did not affect the rate of growth of the fungus, except host leaf decoction agar (HLDA), but influenced its sporulation. Four different media were tested and the highest sporulation was obtained on HLDA followed by potato dextrose agar (PDA), cornmeal agar (CMA) and vegetable soup agar (VSA). For mass production of inoculum (spores and mycelia fragments) liquid medium was found to be more appropriate since large amounts of spores and mycelium could be harvested.