Twelve patients with polysommographic and clinical signs of dopamine-dependent depression (DDD) received, after a short-lasting trial with the dopamine agonist Piribedil, a treatment with oral-tyrosine (3,200 mg/day). On the very first day of treatment a return to mood, as judged by clinical impression and MADRS scores was observed. Sleep recordings performed on nights following days 1, 2, 7 and 8 of treatment showed an immediate improvement of those sleep parameters differentiating the more clearly DDD from other types of depression. More than 50 patients have now been treated successfully for periods ranging from a few months to almost 2 years. This treatment is ineffective in other types of depression.