The potential of Trichoderma spp. fusants for the biocontrol of Rhizoctonia solani was compared with the ability of their corresponding parental strains. Their effect was tested in vitro using two R. solani strains, 509 (AG 2-1) and 618 (AG 4). The highest inhibitions in growth in dual cultures were obtained with the ThF2-1 (89.79%), ThF3-3 (90.55%), ThF4-15 (91.75%) and ThF5-8 (77.67%) fusants on R. solani 509; only ThF2-1 was able to inhibit the growth of R. solani 618 (60.19%). The inhibitory effect on growth was mainly due to diffusible metabolites. Percent mortality and canker level in tomato plants were evaluated in glasshouse experiments where all of the evaluated fusants suppressed plant mortality, but only ThF2-1 and ThF5-8 significantly decreased the canker level.