This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:

(1) To assess whether case management reduces substance use and improves quality of life compared with other forms of treatment, including "treatment as usual", standard community treatment, other psychosocial interventions or waitlist controls;
(2) To evaluate whether case management links patients with the services they need and whether this linkage is related to the effects of case management.
(3) To study whether other potential mediating variables (e.g. length or model of case management, retention in treatment, use of pharmacotherapy) affect case management‐outcomes.