Study Design. Spinal canal decompression at the most prominent of multiple posterior calcified thoracic lesions in a case of X-linked hypophosphatemia was undertaken for treatment and diagnosis purposes, as well as to assess possible nature of the pathophysiology underlying the presenting deficits. Objectives. To discuss the clinical assessment diagnostic and treatment aspects of this rare coincidence of ossification of ligamenta flava in the patient with the skeletal deformities of X-linked hypophosphatemia. Summery of Background Data. The patient with the stigmata and chemical findings of an X-linked hypophosphatemia presented with paraplegia and multiple calcified posterior spinal thoracic lesions. This was studied with magnetic resonance imaging and electrophysiologic studies of the spinal sensory pathways of the legs. These data constituted the preoperative information required to assess later results of surgical intervention. Methods. Presurgical clinical, imaging, and electrophysiologic studies and laboratory and pathologic investigations of the surgical specimens. Results. Resolution of the paraplegia with walking and return to work in a physically demanding job for the last 4 or 5 years of postoperative follow-up after surgical decompression of the spinal cord, only at the worst and highest of the effected spinal levels. Conclusion. The coincidence of X-linked hypophosphatemia and ossification of ligamenta flare has been reported only in two or three cases in the literature. Removal of the offending ossifying lesion is known to result in resolution of the clinical deficits, but similar lesions at other spinal levels are suspected of producing recurrences. The return of function end of the corresponding electrophysiologic correlates indicate a neurono-apractic nature of the neurologic symptoms.