This is a randomized, controlled clinical trial to evaluate the effect of a computerized screening, assessment, and brief intervention on substance use in patients recruited from a primary care clinic. Study participants will be assigned to one of the following 4 study groups: computerized health screening alone (standard care) (SC); computerized assessment-only intervention (CA); computerized assessment followed by a computer-directed motivational intervention (CACI); or computerized assessment followed by a therapist-delivered motivational intervention (CATI). Data regarding substance use, medical and psychosocial functioning, and economic outcomes will be collected.

The investigators hypothesize that patients randomized to CACI and CATI will be more likely to report drug abstinence at the 3-month follow-up visit and will show greater reductions in drug use at 1, 3 and 6 months follow-up than patients assigned to CA or SC. Similarly, patients in the CACI and CATI groups will report greater reductions in HIV risk behaviors, lower rates of medical and psychosocial problems, and increased economic gains at the 6-month follow-up. In addition, patients in the assessment only intervention (CA) will have outcomes superior to those found for SC patients. A cost-effectiveness analysis will also be done comparing economic costs associated with CA, CACI and CATI and their relationship to substance use reductions and related improvements in medical and psychosocial outcomes at the 6 month follow-up.

Inclusion Criteria:

• 18 - 65 years
• Primary care clinic patient

Exclusion Criteria:

• Pregnant