Conclusions drawn from research in the social sciences comparing the quality or quantity of performance under cooperation and competiton stress the advantages of cooperation. This generalization may be premature, however, because of the paucity of experimental analyses investigating variations in competitive conditions. Neglected in particular have been variables that affect reinforcement conditions among competitors. These include performance differences, the basis of reinforcement, reinforcer distribution, and stimuli that indicate the performances of other competitors. These variables provide the basis for a behavioral interpretation of performance under competition. The result is a clearer understanding of the options that are available in instituting competitive contingencies and the areas in which experimental analyses are needed.