A review of the files of familial Mediterranean fever (FMF) confirmed the rarity of patients suffering protracted arthritic attacks and the propensity of the joints, in general, to recover. While 70% of those afflicted suffered bouts of synovitis, only 57 patients (5% of the FMF-population) experienced protracted attacks involving a total of 84 joints, 36 of them knees and 25 hips. Functional and, usually, anatomical integrity was regained in all but 27 joints. Of the 27 joints producing residual incapacity, 21 were hips. Seven hips showed roentgenologically typical aseptic necrosis of the femoral head and 14 only sclerosis and narrowing of the joint space. Eight hips eventually required total prosthetic replacement. We suggest that the poor prognosis of the hip, in contrast to other joints affected by protracted FMF-arthritis, is related not directly to the metabolic aberrration underlying the disease but to attenuation of the arterial blood supply of the femoral head by synovial exudation. Early aspiration of exudate could alter the prognosis by preventing the complication of aseptic necrosis.