Radiographs of the hands of 25 men and 9 women with diffuse idiopathic skeletal hyperostosis (DISH) were compared with age- and sex-matched controls and acromegalic patients. Characteristics of DISH included broadening and "arrowheading" of the distal phalangeal tufts, enlarged sesamoid bones, increased cortical width of tubular bones, prominent enthesopathy in the proximal phalanges, exostoses (particularly at the metacarpophalangeal heads), and new bone in the joint capsule. There was no consistent change in soft-tissue measurements or cartilage width between DISH and control patients. Acromegaly could be differentiated from DISH by the relative lack of enthesopathy, marked soft-tissue changes, and increased cartilage width. Any metabolic factor responsible for the changes in DISH apparently acts primarily on the enthesis and bone but has little effect on soft-tissue or cartilage growth.