'Rapid assessment' (RA) methods have the potential to generate important public health information. This potential is now the subject of debate within the substance use field. Despite this, much remains unknown about the application and outcomes of RAs on substance use, a situation compounded by the absence of published studies. Consequently, we undertook a retrospective review of the use of RA in the substance use field drawing on three methods: literature review (n=300 published and unpublished documents); survey of RA practitioners/commissioners (n=1200 contacts); in-depth expert consultation (n=10 interviews). Study findings indicated: (i) earliest identified RAs were conducted in 1993, with 83 identified studies conducted by 2001; (ii) RAs have been conducted in 70 countries, with seven out of 10 assessments undertaken between 1998 and 2001; (iii) RAs were reported as taking 9-486 days (69 weeks) to complete; and (iv) important outcomes can follow RA on substance use--one in two studies were followed by medical or non-medical interventions, workshops, training, policy change, community participation, network building, or other outcomes (45/83; 54%), whilst more than one in four RAs were followed by medical and non-medical interventions, or policy impact and change (25/83; 30%). In conclusion, we argue that to fully realise the potential of RA in the substance use field, investment has to be made in RA's evidence and knowledge base: in short, a culture of learning, reflection and discussion has to be introduced into a methodology currently premised on rapidity and pragmatism.