Abstract: Thirteen species belonging to six genera of zoosporic fungi, yielding 356 fungal colonies were isolated from 30 soil samples collected from Sohag city. The effect of different levels (0.0, 50.0, 100.0, 150.0 and 300.0 ppm) of the fungicide benomyl on the morphological structures of mycelial, zoosporangia, sexual organs and gemmae of Pythium aphanidermatum and Achlya americana was studied on malt extract medium and callus cultures of garlic. Steroles was determined in garlic callus cultures treated with different levels of benomyl fungicide. GLC analysis showed differences in sterol contents between treated calli of garlic and control ones, which did not meet Achlya americana and Pythium aphanidermatum fungi requirements.