Abstract: Commercial biological control products for the use against plant diseases have to fulfil a broad range of requirements. Besides their efficacy against the targeted plant pathogens major requirements concern the ecological, toxicological and eco-toxicological characteristics of the used antagonists. Consequently, a broad range of criteria has to be considered during the selection of new antagonists. Screening programs can use a stepwise approach to exclude unwanted candidates in an early stage. The antagonists selected with such a screening strategy fulfilling all the major criteria will combine suitable characteristics for registration and marketing as commercial biocontrol products.