This article uses event history analysis to examine certain determinants of dropout from a case management program that serves homeless adults with substance abuse problems. The examined determinants are perceptions of conventional treatment services: (a) client perceptions concerning the value of the conventional services that case managers help them to obtain, (b) the views of use services held by social contacts, and (c) client perceptions of the legitimacy of conventional services. The findings, some of which involve statistical interactions, suggest that clients drop out of case management services more slowly (a) when they favor pursuit of particularly efficacious conventional programs; (b) when they find conventional programs to be of low legitimacy; (c) when, under special conditions, they perceive that conventional services are less caring; or (d) when social contracts do not pressure them. These findings generally imply that clients look to case management services when they are more skeptical about conventional services. The variables predicting dropout from case management poorly predict continuation in conventional substance abuse services, indicating that dropout is linked to perceptions of services in context-specific ways. © 2007 Wiley Periodicals, Inc. J Comm Psychol 35: 583–602, 2007.