The analyses tested the hypothesis that legal pressure is positively related to treatment retention when the effects of age are controlled by statistical techniques. The five treatment modalities examined are used by the Drug Dependence Unit in New Haven, Conn. They are Alpha House, a residential program for adolescents; Daytop, a residential therapeutic community for young adults; Veritas House, a day program for adolescents; Low Intervention Program, an outpatient abstinence and narcotic antagonist program that primarily serves young adults; and Methadone, a program for opiate abusers over the age of 21. This study analyzed the relationships among legal pressure at the time of application and rates of retention and treatment completion for the 404 members of the five treatment modalities from January 1, 1971, through June 30, 1975. Legal pressure was defined to exist if the applicant reported being on probation, on parole, or awaiting trial at the time of application. The study found that the measures of legal pressure were either unrelated or negatively related to retention and outcome in all five treatment modalities. This suggests that nonvolunteer clients are likely to be insufficiently motivated to benefit fully from treatment, and their presence may adversely affect staff morale and the prognosis for volunteer clients. The authors recommend that legal pressure not be used as a basis for assigning applicants to treatment modalities and suggest that treatment outcome might be improved by procedures that deal clinically with motivational differences between volunteers and nonvolunteers. Further, they recommend the establishment of stricter motivational criteria for admitting nonvolunteers and encourage enforcement of existing sanctions against violations of stipulations to treatment. 4 tables and 12 references