Light and electron microscopic examination of bone in reflex sympathetic dystrophy syndrome confirms that vascular disorders play an important role in the genesis of bone lesions. These vascular disorders lead to degeneration of osteocytes and demineralization of bone, with the disappearance of hydroxyapatite crystals. The neo-osteogenesis that follows resembles the different stages of fracture repair, with precocious elaboration of irregular, replacement woven bone, followed by osteoclastic resorption and the laying down of lamellar bone trabeculae. The bone lesions clearly appear to be a consequence of autonomic nervous system circulatory disorders.