summary Immunotherapy with interferon-alfa may induce psychiatric symptoms and disorders: most notably depression. A case history is presented of a 55-year old woman with a manic symptom picture developing during use of interferon-alfa as adjuvant treatment for high risk melanoma. The case illustrates the importance of considering organic or (drug) treatment related causes in the differential diagnosis, when confronted with psychiatric disorders in patients with serious somatic illness. Until now thirteen cases of manic symptom pictures associated with the use of interferon have been described in literature.