Current advances in the study of hypertrophic osteoarthropathy are discussed. An update of the classification of hypertrophic osteoarthropathy is given in which the POEMS (polyneuropathy, organomegaly, endocrinopathy, M protein, and skin changes) syndrome is included among the associated diseases. Cyanotic heart disease is the internal illness most closely linked to hypertrophic osteoarthropathy. The bony alterations at the distal phalanxes and on the periosteum of the tubular bones leave a characteristic and indelible mark that can be diagnosed centuries after the death of the individual. Current thinking suggests that localized activation of endothelial cells by an abnormal platelet population, with the ensuing release of fibroblast growth factors, plays a central role in the pathogenesis of the acropachy. Antiphospholipid syndrome may be a feature of cardiogenic hypertrophic osteoarthropathy. Unraveling the mechanisms of hypertrophic osteoarthropathy may help in understanding the pathogenesis of the associated diseases.