Purpose: The purpose of this paper is to describe the topics covered by coaches assisting teachers implementing a research-based drug prevention program and explore how coaching affects student outcomes. Design/methodology/approach: The All Stars drug prevention curriculum is implemented by 16 urban teachers who received four coaching sessions. Two coaches participated. Coaches are interviewed by investigators to assess topics covered. Students completed pre-test-post-test measures of mediators and substance use behaviours. Findings: The average teacher is coached on 11.7 different topics, out of a total of 23 topics. Coaching topics most heavily emphasized include: introduction and wrap up; time management; general classroom management; teacher's movement around the class; asking open-ended questions; using students' questions, comments and examples to make desired points; general preparation; engaging high-risk youth; reading from the curriculum; implementing activities correctly; focusing on objectives and goals; maintaining a focus on the task; and improving depth of understanding. Seven coaching topics are found to relate to changes in student mediators and behaviour. Research limitations/implications: The current study is exploratory. Future research should explore how teachers develop the particular skills required by prevention programs and how coaches can assist them. Practical implications: Five levels of skill development are postulated, which coaches may address: fundamental teaching skills, mechanics of program delivery, development of an interactive teaching style, effective response to student input, and effective tailoring and adaptation. Originality/value: The paper is one of a very few studies that explores how coaching impacts outcomes in substance abuse prevention. (Contains 5 tables.)