Fifteen winter (previous) crops were evaluated as to their effects on pathogenicity of M. phaseolina on cotton cultivars Giza 75, Giza 80, Giza 83, and Giza 85 under  greenhouse conditions. Onion and garlic were the best performing crops in controlling M. phaseolina. This superiority was attributed to the following reasons: first, they were the most effective crops in suppressing M. phaseolina during the postemergence stage as they decreased seedling mortality by 89.89 and 85.39%, respectively, regardless of the cotton cultivar. Second, onion was one of the two most effective crops in increasing the percentage of the surviving seedlings of Giza 80,while garlic and onion were the most effective crops in increasing survival of the other cultivars. Third, garlic significantly improved plant height of Giza 80 seedlings. Garlic and onion significantly increased plant height of Giza 85 seedlings. Fourth, garlic significantly improved dry weight of Giza 80 and Giza 83 seedlings by 57.66 and 99.04%, respectively. The effect of depth (5, 10, or 25 cm) of M. phaseolina inoculum, originating from artificially infested sorghum grains, on charcoal rot incidence of cultivar Giza 75, were studied in30-cm-diameter clay pots. Sallow placement of inoculum was accompanied by greater isolation frequency than placement of inoculum deep in soil; furthermore, M .phaseolina had no detrimental effects on cotton growth up to the time of flowering when inoculum was placed at a depth of 25 cm prior to planting.