This chapter examines the extent to which relationships are structured in particular ways by the partners' personality characteristics and their compatibility. Three models pertaining to the psychological and interpersonal roots of the development and deterioration of intimate relationships have been proposed by social scientists. (1) The disillusionment model portrays lovers as driven to put their best foot forward and as inattentive to each other's – and the relationship's – shortcomings until after the wedding knot is tied (Huston, 1994; Swann, De La Ronde, & Hixon, 1994; Waller, 1938). (2) The perpetual problems model, in contrast, suggests that the interplay between the partners' dispositions gets played out during courtship and that, as a consequence, the partners develop feelings and views about each other that reflect the underlying, relatively stable, psychological infrastructure of the relationship (Burgess & Wallin, 1953; Heaton, Albrecht, & Martin, 1985; Huston, 1994; Surra, 1990). (3) The accommodation model posits that when problematic dispositions or incompatible desires surface in a relationship they initially create disappointments and antagonisms; over time, however, partners who remain together maintain a satisfactory bond by adapting their expectations or otherwise coming to terms with their situation (Bernard, 1964; Heaton et al., 1985; Rusbult, Verette, Whitney, Slovik, & Lipkus, 1991).