Background: Recently, reports from North America have indicated that the intravenous infusion of ketamine hydrochloride (an N-methyl-daspartate receptor antagonist) results in a sudden and robust improvement of depression symptoms. Objective: To corroborate antidepressant effectiveness of IV ketamine in a patient with a co-occurring substance use disorder for the first time in a European clinical setting. Design: Open label trial Methods: A 55-year-old male subject with a treatment-resistant major depression and a co-occurring alcohol and benzodiazepine dependence received an intravenous infusion of 0.5 mg/kg ketamine over a period of 50 minutes. Effects were assessed by means of a clinical interview, the 2 1 item Hamilton Depression Rating scale (HDRS), and the 21-item Beck Depression Inventory (BDI) at baseline, 1 hour, 1 day, 2 days, and 7 days after intervention. Results: Following the administration of ketamine the subject experienced a significant improvement of his symptoms peaking on the 2(nd) day post infusion (HDRS from 36 to 16; -56.6%, BDI from 26 to 9; -65.4%). The subject first reported improvements 25 min. into the infusion and continued to describe positive effects throughout the subsequent 7 days. Conclusion: Ketamine not only seems to have strong antidepressant effects but also to act very swiftly. These actions were unaffected by an alcohol or benzodiazpine dependence.