The great majority of interest structures for two interacting parties do not fit any of the classes discussed in Chapter 4. For example, among 2 x 2 primitive games, only 49 of all 881 structures fit such categories. All of the rest are mixedmotive games, in which there is some combination of common and opposed interests. Our discussion of mixed-motive games in the present chapter will divide them into three further categories: (1) those with a natural outcome which is Pareto-optimal, (2) those with a natural outcome which is Pareto-deficient, and (3) those without a natural outcome.