After elimination of infectious causes, neoplastic causes and the systemic autoimmune disease of connective tissue, a patient with high fevers over 39 °C was diagnosed with Still's disease. High doses of prednisone led to resolution of symptoms, however after reducing the doses of prednisone to 15 mg, high fevers over 39 °C returned, as well as joint pains. The high doses of prednisone led to decompensation of diabetes mellitus even with 4 daily insulin dosages. Therefore it was proceeded to regular subcutaneous administration of anakinra once a day. Anakinra enabled the reduction of prednisone to as much as the currently administered 2.5 mg a day, but it has not so far allowed for removing glucocorticoids from the treatment completely. Activity of the disease is shown by the findings within the FDG-PET/CT examination. At the time of maximum activity of the disease there was distinct lymph-adenopathy with pathological accumulation of FDG visible as well as increased accumulation of FDG in the hema-topoietic bone marrow. As the disease activity decreased, the size of nodules regressed and FDG accumulation in both the lymphatic nodes and bone marrow declined. FDG-PET/CT is a suitable method for monitoring the activity of Still's disease.