This study aims to study and implement active referral of heroin users from a syringe exchange programme to evidence-based treatment for heroin addiction. Patients are randomized to either a strength-based case management intervention or a control group, while both groups receive referral to medical investigation for inclusion in substitution treatment for heroin addiction. The hypothesis is that syringe exchange can be used for referral to effective treatment, and that a strength-based intervention can increase the number of patients who are successfully referred and enter treatment.