While substance use disorders have long been recognized as chronic relapsing conditions, it has mainly been in the last two decades that clinical researchers have been systematically attending to the nature and processes of relapse. These efforts have led to the development of a variety of psychological and psychobiological models of relapse. These models are summarized in the present article, with particular attention placed on each model's basic principles and on the precipitants of relapse predicted by the respective models. The delineation of these models may help facilitate subsequent cross-referencing and cross-fertilization of thinking in this important area.