Reasons for premature termination of outpatient substance user treatment were evaluated from client and clinician perspectives using qualitative (focus groups) and quantitative (survey) methods in a pilot study (N = 44). The sample consisted of clients (n = 22), the majority of whom were male (73%) and African American (50%) or Caucasian (41%). The sample of clinicians (n = 22) were predominantly female (64%), and Caucasian (52%) or African American (24%). The most frequently endorsed reasons for leaving treatment were related to individual rather than program characteristics with heavy drug or alcohol use, transportation or financial problems, and ambivalence about abstinence being highly rated by both clinicians and clients. Survey results indicated that clinicians more frequently attributed treatment dropout to individual- or client-level factors than did clients. Focus group ratings indicated that clinicians felt client motivation and staff connection issues were primary reasons for dropout, whereas clients indicated social support and staff connection issues. The findings suggest that the development of early therapeutic alliance and active problem solving of potential barriers to treatment attendance may influence treatment retention.