In order to study the biological control of soil-borne disease of sesame, antagonistic isolates of Trichoderma , Bacillus sand streptomyces to Fusarium oxysporum and Rhizoctonia solani were isolated from the rhizosphere soils of sesame plants and some other habitats. Out of the isolates of microorganisms collected a strain of Trichoderma viride was selected as a biological control agent for the study and its effect on the control of damping-off and the seedling growth of sesame was investigated. The results obtained are as follows: 26 percents of Bacillus spp. isolated from the rhizosphere soil of sesame plants showed antagonism to two pathogenic fungi. Important species were B. Subtilis and B. polymyxa. Streptomyces species isolated from the rhizosphere soils of sesame lysed the cell wall of hyphae and conidia of F. oxysporum and reduced conspicuously the formation of macroconidia and chlamydospores of the fungus. 84 percents of Trichoderma spp. isolated from the rhizosphere soil of sesame plants were antagonistic to F. oxysporum and 60 percents of the isolates were antagonistic to both F. oxysporum and R. solani. Trichoderma viride TV-192 selected from antagonistic isolates of Trichoderma spp. was highly antagonistic to F. oxysporum and soil treatment with the isolate reduced notably damping-off of sesame. T. viride TV-192 showed better growth in crushed rice straw, barley straw and sawdust media than F. oxysporum. Sawdust was selective for the growth of T. viride. Supplementation of wheat bran and mixtures of wheat bran and sawdust inoculated with T. viride TV-192 in the soil reduced remarkably damping-off of sesame by F. oxysporum but high density of the fungus TV-192 caused the inhibition of seed germination and seedling growth of sesame. Inhibitory effects of Trichoderma species on seed germination and seedling growth of sesame were different according to the isolates of the fungus. Normal sesame seedlings on the bed treated with the fungus showed better growth than not treated seedlings.