In October 2013, a 46-year-old female patient presented for psychiatric consultation. She was diagnosed with major depression which had developed gradually in the past 10 years. She was treated in an out-patient unit with 3 different antidepressant drugs (fluoxetine, escitalopram, bupropion) at adequate dosages and duration with no antidepressive effect. The patient was admitted to hospital where additional investigations were done to exclude organic causes for depression. Treatment consisted of electroconvulsive therapy, combining antidepressant drugs (venlafaxin, bupropion, agomelatine) with different modes of action and cognitive behavioural psychotherapy. The effects of treatment were unsatisfactory and during the half-year period the depressive syndrome worsened even further and she was rehospitalized for treatment with intravenous administration of ketamine. She received 5 intravenous ketamine (0.3–0.5 mg/kg of body weight) infusions administered over 40 minutes with a 3-day interval. A rapid onset of the antidepressant effect was seen and partial response was maintained over a 6-month period.