Back pain--a common complaint familiar to all physicians--can be either a manifestation of musculoskeletal dysfunction or a symptom of a more serious underlying disease. Unfortunately, the diagnosis can be difficult, and back pain that is not resolved by conservative treatment requires aggressive investigation. The author presents the case history of a 17-year-old patient whose back pain had been extensively evaluated by a series of specialists to no avail until further workup revealed the problem to be Ewing's sarcoma. The steps required to diagnose elusive back pain are presented, together with a brief discussion of cauda equina syndrome and conus medullaris syndrome, components of both of which were found in this patient.