The field of clinical behavior analysis is growing rapidly and has the potential to affect and transform mainstream cognitive behavior therapy. To have such an impact, the field must provide a formulation of and intervention strategies for clinical depression, the "common cold" of outpatient populations. Two treatments for depression have emerged: acceptance and commitment therapy (ACT) and behavioral activation (BA). At times ACT and BA may suggest largely redundant intervention strategies. However, at other times the two treatments differ dramatically and may present opposing conceptualizations. This paper will compare and contrast these two important treatment approaches. Then, the relevant data will be presented and discussed. We will end with some thoughts on how and when ACT or BA should be employed clinically in the treatment of depression. (Contains 1 table and 4 footnotes.)