If a predator crops preys certain ages in preference to others, it may be acting as an agent of selection, causing genetic change in the prey population. A model of life-history evolution was adapted to investigate some selective consequences of several patterns of age-specific predation. The model allows allocation of resources to reproduction, growth and maintenance in an age class i to be varied. Subject to several assumptions, increasing predation on individuals younger than i leads to selection for lower rates of reproduction at age i. Increasing predation on individuals older than and/or equal to i leads to selection for greater rates of reproduction. If individuals from both these age ranges are cropped, the optimal rate of reproduction may either increase or decrease. The only circumstance under which no change occurs arises if all individuals irrespective of age are liable to be cropped, or if the effects of predation on younger and older age classes exactly cancel one another. The implications of these results to the management of populations exploited by man are discussed.