Behaviour therapy is now beginning to assess the social validity, along with efficacy, of its treatments. Literature dealing with the social validity of parent-training programs is reviewed. The aim of this investigation was to obtain acceptability ratings of the “time out” procedure from the perspective of behaviour problem and non-problem children. The study looked at acceptability ratings of five maternal behaviours/disciplinary techniques (permissiveness, physical punishment, directed discussion, quiet time, time out) across four different situations (non-compliance with an initiating instruction, aggression toward others, non-compliance with a terminating instruction, non-compliance with known rule) by samples of clinical (problem behaviour) children and control children. Both groups were alike in rating permissiveness as less acceptable than any of the other behaviours across most situations and rating it as unacceptable in absolute terms. Time out was rated equally acceptable with physical punishment, directed discussion and quiet time. The results support previous findings that young children prefer interventionist to permissive parents, including the use of exclusionary time out. In a second study, ratings were taken from two clinical groups, treatment and waitlist, both at pre- and post-treatment. Despite large individual differences in the treatment group, no change in acceptability ratings was found at post-treatment. Thus, experiencing time out did not change the children's evaluation of this procedure. Possible reasons for these findings and their practical implications are discussed.