Purpose: A literature review was conducted to evaluate the effectiveness of external contributors (anyone other than a teacher at the school) in delivering school-based drug, alcohol and tobacco education (substance use education) programmes. Design/methodology/approach: The review focused upon literature published from 1990 onwards in English. Published reports were identified via electronic searches, supplemented by hand searching of relevant journals. Relevant organisations and individuals were contacted to identify low circulation, difficult to acquire (grey) literature. Judgements were made of methodological quality and only reports judged to be methodologically sound or better are included in this paper. Findings: A total of 114 reports were included in the review (53 published, 61 unpublished), 42 of which were considered methodologically sound. In total 16 types of contributor were evaluated (although only nine in methodologically sound studies) including nurses, police officers, theatre groups, peers and researchers. There was insufficient evidence to judge a particular type of contributor as most effective at delivering substance use education programmes in terms of behavioural, knowledge, intention or mediating outcome measures, although peers show promise. However, process data revealed that pupils enjoy content delivered by external contributors, which is important, as pupils are more likely to attend to information that is enjoyable. Practical implications: The paper finds that external contributors should be used in a supplementary role in substance use education in a manner reflecting their expertise, when that expertise maps onto the aims and content of the drug education planned by the school. Originality/value: With over 80 percent of schools in the USA and the UK using external contributors to deliver substance use education, this paper highlights best practice guidance for their use. (Contains 4 tables.)