Fixed variables included demographic and background characteristics that had been used to predict client retention and outcomes in previous research. Dynamic variables included circumstances under which clients joned problems and their motivations for seeking drug treatment. The analysis revealed that although both fixed and dynamic variables predicted client retention, the strongest predictors were two dynamic variables. One was predictions by exaddict interviewers of whether clients would stay in the program long enough to benefit from treatment. The other was whether clients had spent most of their time with large groups of people, as opposed to spending most of their time with small groups or alone, before using drugs. Findings indicated that program and treatment variables need to be considered along with client variables to improve understanding of retention and improve it in therapeutic communities and other drug treatment programs. Tables and 34 references (Author abstract modified)