Feedback-based brief interventions for alcohol use have been shown to be highly effective with undergraduate populations. However, there has been little research on their effectiveness with community treatment populations, who typically have higher levels of dependence, comorbidity, and chronicity. The effectiveness of an assessment/feedback brief intervention to reduce alcohol use versus an assessment only condition with no feedback component was investigated in a community treatment setting with patients (N = 87) characterized by high levels of long-term dependency on alcohol and drugs, high levels of comorbidity, ethnic diversity, and low socioeconomic status. It was hypothesized that randomization to a condition receiving brief individualized feedback would reduce alcohol consumption and increase motivation for substance use treatment, versus randomization to a condition the same assessment but no feedback. Repeated measures ANOVAs and ANCOVAs were used to examine primary outcome variables obtained from the Addiction Severity Index (ASI; McLellan et al., 1992) of drinking quantity and frequency, and motivation for treatment. Results suggested that participants who received the feedback showed substantial reductions in number of drinking days at follow-up 30 days post-intervention (i.e. 30 days from the date of the intake). However participants who received the feedback and those who did not did not differ on other outcomes at follow-up, including days of heavy drinking, motivation for treatment, or drug use frequency. Findings may be influenced by the decision to seek help, assessment reactivity, or treatment effects as on nearly all outcome measures participants in both conditions showed greatly improved outcomes at follow-up.