Objective. We investigated the concept of ‘quality of assertive outreach programmes for severely impaired substance abusers’ with the aim of developing a conceptual framework as the basis for an assessment instrument. Design. We held a concept-mapping session with 13 experts in 2003. Fifty measurable elements of quality were mentioned and rated in terms of relative importance on a Likert-type response scale. Subsequently, the experts grouped the statements that were similar in content. The resulting concept map and additional interpretation made up the final quality framework. Setting/study participants. Theoretical sampling was used to select Dutch managers, team leaders, and service providers from different assertive outreach delivery systems for substance abusers. Variation in both perspective and region was reflected in the sample. Results. Nine aspects of quality were formulated: preconditions for care, preconditions for service providers’ work, relationship to regular care, service providers’ activities and goals, service providers’ skills, the role of repression, optimal care for the client, goals of assertive outreach, and nuisance reduction to society. Each aspect was presented using a selection of measurable elements. Conclusions. According to the experts, optimal assertive outreach depends on a broad range of aspects that were later classified in three regions: structure, process, and outcomes. Saturation of the elements has not been proved so far. Nevertheless, it is promising that the framework’s regions are supported by theory and that it is largely in accordance with clients’ perspectives on assertive community treatment.