white mold caused by sclerotinia sclerotiorum may severely damage vegetables grown in greenhouses. to develop a biological control program for this pathogen proper antagonists are needed. this work aimed to select efficient fungi antagonists for controlling s. sclerotiorum on cucumber (cucumis sativus) grown in greenhouses, and to evaluate the effect of the antagonist on the growth of the vegetable. an isolate of s. sclerotiorum obtained from cucumber and 112 fungi isolates belonging to four genera were used: trichoderma, fusarium, penicillium, and aspergillus. for the in vitro experiment, the cellophane method was used and eight trichoderma virens isolates were selected that had inhibited the pathogen growth by 94 to 100%. greenhouse experiments used sterilized and non-sterilized substrate in plastic cups and non-sterilized substrate in plastic bags. the substrate was inoculated with s. sclerotiorum and the eight isolates of t. virens were used as antagonists. all eight isolates controlled damping-off of plants caused by s. sclerotiorum, but the effect on cucumber growth varied according to the isolate and the substrate treatment.