The positive relationship between time spent in substance-abuse treatment and improved outcomes has led to a significant interest in interventions that encourage substance abusers to remain in treatment. Case management has been tested for its role in both encouraging continued participation and directly affecting desired outcomes. This article reports findings from an ongoing longitudinal study that randomly assigned more than 600 substance abusers entering treatment to either a usual primary and aftercare drug treatment services group or a usual services plus enhanced strengths-based case management group. A cluster analytic technique was used to identify patterns of participation in post-primary treatment (i.e., aftercare and case management), among those clients in the enhanced group. Three distinct clusters emerged that suggest a prominent role for this model of case management as either an adjunct or an alternative to conventional treatment. Tables, references