BackgroundProblem alcohol use is common among illicit drug users and is associated with adverse health outcomes. It is also an important factor in poor prognosis among drug users with hepatitis C virus (HCV) as it impacts on progression to hepatic cirrhosis or opiate overdose in opioid users.ObjectivesTo assess the effects of psychosocial interventions for problem alcohol use in illicit drug users (principally problem drug users of opiates and stimulants).Search methodsWe searched the Cochrane Drugs and Alcohol Group trials register (November 2011), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 11, November 2011), PUBMED(1966 to 2011); EMBASE (1974 to 2011); CINAHL (1982 to 2011); PsycINFO (1872 to 2011) and reference list of articles. We also searched: 1) conference proceedings (online archives only) of the Society for the Study of Addiction (SSA), International Harm Reduction Association (IHRA), International Conference on Alcohol Harm Reduction (ICAHR), and American Association for the Treatment of Opioid Dependence (AATOD); 2) online registers of clinical trials, Current Controlled Trials (CCT), Clinical Trials. org, Center Watch and International Clinical Trials Registry Platform (ICTRP).Selection criteriaRandomised controlled trials comparing psychosocial interventions with another therapy (other psychosocial treatment, including non-pharmacological therapies or placebo) in adult (over the age of 18 years) illicit drug users with concurrent problem alcohol use.Data collection and analysisTwo review authors independently assessed risk of bias and extracted data from included trials.Main resultsFour studies, 594 participants, were included. Half of the trials were rated as having high or unclear risk of bias. They considered six different psychosocial interventions grouped into four comparisons: (1) cognitive-behavioural coping skills training versus 12-step facilitation (N = 41), (2) brief intervention versus treatment as usual (N = 110), (3) hepatitis health promotion versus motivational interviewing (N = 256), and (4) brief motivational intervention versus assessment-only group (N = 187). Differences between studies precluded any pooling of data. Findings are described for each trial individually:comparison 1: no significant difference; comparison 2: higher rates of decreased alcohol use at three months (risk ratio (RR) 0.32; 95% confidence interval (CI) 0.19 to 0.54) and nine months (RR 0.16; 95% CI 0.08 to 0.33) in the treatment as usual group; comparison 3 (group and individual format): no significant difference; comparison 4: more people reduced alcohol use (by seven or more days in the past 30 days at 6 months) in the brief motivational intervention compared to controls (RR 1.67; 95% CI 1.08 to 2.60).Authors' conclusionsVery little evidence exists that there is no difference in the effectiveness between different types of interventions and that brief interventions are not superior to assessment only or treatment as usual. No conclusion can be made because of the paucity of the data and the low quality of the retrieved studies.