This prospective longitudinal study examined the influence of patients' perceptions of their counselors on their lengths of stay in treatment and subsequent treatment outcomes. Patients (N = 511) were recruited from 19 substance abuse treatment programs in Los Angeles County. While in treatment, patients rated their counselors on 14 aspects (e.g., empathy, directiveness); 1 year later they were interviewed for follow-up outcomes. Multiple regression analyses were conducted using patients' ratings of their counselors to assess the impact of these ratings on treatment retention and follow-up outcomes (i.e., severity of alcohol use, drug use, and psychiatric status as measured by the Addiction Severity Index). Results revealed that patients' positive perceptions of their counselors were significantly associated with a longer length of stay in treatment for the outpatient drug free/day treatment and residential treatment subsamples. Patients' positive perceptions were also significantly associated with better psychiatric functioning at follow-up, but had a limited relationship to severity of alcohol use and no relation to severity of drug use.