Retrospective case series for the last five years have focussed the attention of the authors on some clinical and biological patterns of adult onset Still's disease. Its diagnosis is made difficult because of the great diversity of clinical and biological signs. Organ failures complicate sometimes the disease, and may be fatal. Major high levels of plasma ferritin associated with an haemophagocytic syndrome occur in 20 percent of the acute cases: this association could eventually respond well to an immunodepressive therapy.