 The Quit Using Drugs Intervention Trial QUIT will be the first randomized controlled trial in the U.S. that is powered to detect the effect of a primary care clinician delivered brief intervention protocol for reducing at risk drug use and drug-related harm among low-income adult patients ages 18 and older at multiple safety net clinics in Los Angeles County. For this small trial, we will sample patients with at risk use of drugs marijuana, crackcocaine, amphetaminesmethamphetamines, inhalants, sedatives or sleeping pills, hallucinogens, and opiates, the most commonly used serious drugs among patients at our clinic sites. At risk drug use is defined in this study as current use past 90 days of drug measured as a self-reported total score of 4 to 26 on the WHO Alcohol Substance Involvement Screening Test ASSIST. A total of 7,000-8,000 patients will be approached for screening to yield a 3-month effective sample size of 245 eligible patients per condition 1 an intervention condition involving drug use health education or 2 a control condition involving care as usual. In the intervention condition, very brief less than 5 minutes clinician advice regarding quitting drug use will be followed by two 2 and 6 week post-visit drug health education sessions on quitting drug use and cautioning against use of other at risk substance use such as alcohol and tobacco. Patients assigned to the control condition will receive standard care for drug use at the baseline visit with their clinician. Follow-up assessments will be conducted at 3 month post-randomization. The framework for the QUIT project is the Social Action Theory, and the brief intervention protocol is based on NIDAs principles on prevention research and the utility of the 5 As approach for assisting behavioral changes among patients Ask, Advise, Assess, Assist, Arrange in the clinic setting. If found to be effective in the community health center setting, this clinician and telephone drug-use health education program could become a model for health promotion activities. that would be expanded to all at risk substance use and shared between community health centers. 