The purpose of this article is to present a new model, coined “successive cohort design” (SCD), for developing and testing psychosocial therapies, and to illustrate the model with a description of a specific treatment developed. Using this SCD, we developed an outpatient Behavioral Couple Therapy for Drug Abuse (BCTD) manual under a National Institute on Drug Abuse Stage 1 Behavioral Therapy Development grant. After a start-up period during which an initial manual was written, 3 cohorts of couples were treated in weekly, 6-month outpatient, manual-guided BCTD, over a 2.5-year period. After each sample wave, the assessment and/or treatment protocol was revised based on our experience of treating that cohort. In total, 24 couples were treated, 12 in the first cohort, 6 in the second, and 6 in the third. Participants were assessed at baseline and 6 and 9 months later. The outcome data are reported elsewhere.1 This SCD for Stage 1 research is offered as a useful and viable therapy development model.