summary According to the classical definition, someone with the Ganser syndrome gives 'approximate' answers, i.e. answers that are beside the point, has lowered consciousness, displays somatic conversion symptoms and suffers from pseudo-hallucinations. On the basis of the case of an 80- year-old female patient who gave approximate answers and by means of a systematic review of the literature, we give the differential diagnosis of the Ganser syndrome. The causes seem to be largely organic.