With recent advances in the behavioral treatment of depression and growing dissatisfaction with medical and cognitive interventions, a resurgence of interest in behavior analytic treatment of depression has occurred. Currently, several behavioral and cognitive behavioral models of depression exist. In reviewing these models, certain agreed upon environmental factors emerge. In this paper, we explore five factors related to a behavioral treatment of depression. Three of these factors view depressive behavior as a bi-product of person-behavior-environment interaction. These are (1) lack of response contingent reinforcement of behavior, (2) too much punishment of behavioral responses, and (3) loss of effective operant behavior. In addition, two models view depressive behavior as operant behavior as controlled by (4) positive reinforcement and/or (5) negative reinforcement. Two final factors to consider are (1) depressive behavior develops as a failure to develop or an over reliance on rule governed behavior and (2) environmental factors that precipitate depression may be viewed as establishing operations. Each of these factors will be explored as well as multiple combinations of these factors in the generation and continuation of depression. Key words: Depression, Functional Assessment, Clinical Behavior Analysis, & Behavioral Models of Depression. ********** In the 1990's, a resurgence of interest in behavioral theories of depression occurred. This resurgence derived from the establishment of clinical behavior analysis as a vibrant adjunct to applied behavior analysis (Dougher, 1993; 1994; 2000) with active theoretical and empirical investigations and treatment developments relevant to outpatient psychotherapeutic treatment of depression. In addition, a component analysis of cognitive-behavior therapy for depression showed that the behavioral component (behavioral activity scheduling was referred to as behavioral activation) was sufficient to explain recovery from initial depression (Jacobson et al., 1996) and at follow up (Gortner, Gollan, Dobson, & Jacobson, 1998). The cognitive component of treatment appeared to add little to the overall outcome. These findings renewed interest in behavioral approaches to depression treatment (Hollon, 2001; Jacobson & Gortner, 2000) and sparked development of a complete Behavioral Activation approach (Martell, Addis, & Jacobson, 2001; also see Kanter, Callaghan, Landes, Busch, & Brown, 2004). Other clinical behavior analytic approaches to depression have also been evaluated, including Acceptance and Commitment Therapy (Zettle & Hayes, 1986; Zettle & Rains, 1989) and Functional Analytic Psychotherapy (Kanter, Schildcrout, & Kohlenberg, in press; Kohlenberg, Kanter, Bolling, Parker, & Tsai, 2002). The above sets the stage for a re-analysis of behavioral theories of depressive behavior (e.g., Bolling, Kohlenberg, & Parker, 2000; Dougher & Hackbert, 1994; 2000; Ferster, 1973; Hoberman & Clarke, 1993; Kanter et al., 2004; Lewinsohn, 1974). In review of current behavioral models of depression, we found that several factors were highlighted. First, early models incorporated Skinner's (1953; 1974) stance that feelings such as depression are respondent bi-products of behavior-environment interactions. For example, failure to achieve sleep as a reinforcer for insomniacs might produce depressive symptoms. Subsequent models focused on direct functional aspects of depression. While many of the early pioneers of behavioral approaches to depression became focused on cognitive phenomena after initial investigations, this behavioral work remains an excellent starting point for current theory exploration. In particular these models emphasized depression as a function of positive reinforcement deprivatio n, either in terms of low density of positive reinforcement (Ferster, 1973) or low rates of response-contingent positive reinforcement (Hoberson & Lewinsohn, 1985; Lewinsohn, 1974, 1975). …