Criteria for ranking potential target pest arthropods to which biological control might be applied are discussed and organized into a numerical rating system. Candidate projects are rated in three separate areas: biological control feasibility, economic assessment, and institutional/administrative assessment. Separate ranking in each of these areas allows economic and political factors influencing a project to be distinguished from biological factors. The use of this index allows pest complexes across numerous crops to be ranked, so that overall biological control priorities for a state or country can be identified in an objective manner and used as a basis for planning long-term programs of biological control implementation.