Seventeen patients with early rheumatoid synovitis underwent synovial biopsy to assess the interrelationship between both ferritin (the intracellular iron storage protein) and Perls' positive iron (ferric iron in loose combination with protein), on the activity and course of rheumatoid disease. The amount of ferritin was associated to a significant degree with the activity of the disease at the time of biopsy, but showed no relation to the way the disease progressed over the following year. In contrast, the amount of Perls' iron bore no relation to the activity of the disease at biopsy, but its presence was associated with persistent disease. It is argued that this association is direct, that ferritin production may fail in a population of synovial macrophages, and that Perls' ferric iron may either be reduced to the ferrous form and promote the formation of toxic free radical species, or stimulate collagenase and prostaglandin release from synovial macrophages.