Fifteen isolates of Trichoderma spp., two isolates of Aspergillus spp., and four isolates of Penicillium spp. were evaluated under field conditions in Assiut and Mallawy as to their efficiency in suppressing cotton seedling damping-off. Seeds of cotton cultivar Giza 83 in both locations were treated with a dry powder of antagonist-sorghum mixture at a rate of 10 g/kg seeds. Of the twenty-one isolates, isolates nos. 3, 9, 10 and 11 of Trichoderma spp. and isolate no. 18 of Penicillium sp. were effective in increasing stand and yield in both locations. Many of the other isolates were effective in increasing both stand and yield; however, their efficiencies were restricted to one location- that is, their performance lacked stability. It is noteworthy that some isolates of the biocontrol agents were as effective as or even more effective than Rizolex T in suppressing the disease and increasing yield in Assiut or Mallawy.