Considerable success in biological control has been achieved by manipulating natural enemies to control insect pests. Ecological theory and experience suggest that species which might compete with pests could be manipulated to effect biological control of the pests. A conceptual model is presented that can aid in identifying pests suitable for biological control by non-pest competitors. Such pests must require, in addition to the resource(s) we wish to protect from damage, at least one resource which is “neutral” from our economic and/or social perspective. I argue that competition for the neutral resource could lower the pest's abundance and hence reduce damage to the protected resource(s). Examples of suitable pests and methods of manipulating competitors are discussed. Biological control by non-pest competitors may be as safe and effective as biological control with predators and parasites, but it may not be as permanent in evolutionary time.