Barriers to participation in treatment were proposed as a basis for dropping out of treatment among children seen in outpatient therapy. Families (N= 242) of children referred for treatment for oppositional, aggressive, and antisocial behavior participated. The main findings were that (a) barriers to participation in treatment contributed significantly to dropping out of therapy;(b) perceived barriers to treatment were not explained by family, parent, and child characteristics that also predicted dropping out; and (c) among families at high risk for dropping out of treatment, the perception of few barriers attenuated risk. Parent perceptions of the difficulties of participating in treatment (including stressors and obstacles associated with treatment, perceptions that treatment is not very relevant, and a poor relationship with the therapist) influenced who dropped out.(PsycINFO Database Record (c) 2016 APA, all rights reserved)