The authors report eleven new cases of adult Still's disease diagnosed during the last 5 years. This rare, though not exceptional, disease of unknown pathogenesis is difficult to diagnose in the absence of specific sign; it is in fact diagnosed by elimination. The clinical, laboratory and anatomical findings, as well as the treatment and outcome of these 11 cases are described, and this is followed by a discussion of the nosological, therapeutic and above all prognostic problems raised by the disease.