Acamprosate is registered in the Benelux for the treatment of alcohol dependence. In a randomised, placebo-controlled, double-blind study in 262 subjects from 22 treatment centres in the Benelux countries, the effect of acamprosate as a supplement to the existing out-patient psychosocial intervention was studied on relapse after detoxification over a period of 6 months. Acamprosate had a clear positive effect on relapse prevention. Subjects in the acamprosate group completed treatment more frequently (41 vs. 31 %) and on average remained in treatment for longer (102 vs. 88 days). Patients in the acamprosate group relapsed later (after 45 vs. 15 days), were abstinent longer (61 vs. 43 days) and were more often abstinent for the entire duration of the 6-month treatment (20 vs. 10%). In the acamprosate group, 11% consumed no alcohol throughout the study period, while in the placebo group this was the case only in 5%; however, on account of the small numbers, this difference was not statistically significant. The therapeutic advantage of the acamprosate-treated patients was still present 6 months after treatment. The drug was generally well tolerated, and no serious complications occurred during the study. A major problem was the large number of subjects in both the experimental as well as the control group who did not complete treatment. It is concluded that acamprosate could be a useful adjuvant to psychosocial treatment.