The question of the longitudinal health and stability of a marriage may seem, at first blush, to be the same question as what makes some marriages happy whereas others are unhappy. In this chapter, the longitudinal question is introduced, particularly related to issues of marital stability. Previous research on marital dissolution rarely has been based on prospective research studies. Previous prospective studies have not done very well in predicting dissolution, nor have they yielded a consistent theoretical formulation of the marital processes that may be related to stability or dissolution. First, a cascade model of marital dissolution is presented that links work on marital unhappiness to work on marital dissolution. Second, a balance theory of marriage yields a first cut at prediction of a trajectory toward dissolution versus stability. Process cascades also are explored that are related to the cascade toward marital dissolution.