The purpose of this study is to report the case of a 34 year old patient, from Zaïre for whom a wrong diagnosis could have been fatal. Recent events in his affective and professional life, associated with typical symptoms, suggested a major depression. However after two months of being admitted a psychiatric ward, the resistance to treatment together with some biological data suggested further investigations. They revealed a subacuse meningo-encephalitis of parasitological etiology. The psychiatric aspects of trypanosomiasis commonly known by clinicians in Africa justifies, in patients from that continent, a systematic test for trypanosomiasis.