The adult onset Still disease is a systemic disease of an unknown etiology. As a separate entity, it was described firstly in 1971. The diagnosis is problematic and based upon special criteria. In this study, we present the cases of two patients with adult onset Still's disease, causing several serious differential-diagnostic problems. In the beginning of the disease a high, remittent-intermittent fever was present which reacted well to salycilates. Almost simultaneously, a characteristic, confluent, no itching rash appeared on the trunk and limbs. Pain of little joints of the hands was an early symptom of the disease in both of the cases. Before the final diagnosis, the possibility of any infectious diseases, haematologic malignancies or other autoimmune disease had to be excluded. The aim of this work was to show an overall, up-to-date picture of the disease based on two typical cases.