The competitive saprophytic fungus Ulocladium atrum was selected on the basis of its antagonistic potential for the control of grey mould caused by the necrotrophic pathogen Botrytis cinerea. Field trials were carried out to asses the efficacy of U. atrum as a biocontrol agent against B. cinerea in grapevine. The results demonstrated that under moderate disease pressure U. atrum had the potential to control grey mould, whereas under high disease pressure the efficacy was not sufficient to substitute the use of fungicides completely.