During a 16-year period 672 patients were admitted to the Columbia Presbyterian Medical Center with spastic paraplegia-paraparesis (SPP) as a prominent finding. Group I. 520 patients (77.3%) had either a familial disorder, sensory findings, other neurological signs, or a diagnosis obvious on admission by history, examination or plain spine roentgenograms. Group II. In 108 patients (16.2%) diagnosis was reached after more extensive investigation. In 78 of these a cause other than multiple sclerosis was found including spinal cord tumor, arteriovenous malformation and cervical spondylotic myelopathy. Thirteen patients had probable multiple sclerosis on the basis of additional signs emerging, and 17 were considered to have possible multiple sclerosis on the basis of elevated CSF gamma-globulin. Group III. In 44 patients (6.5%) no cause for SPP could be found. Diagnostic considerations for this group included amyotrophic lateral sclerosis, multiple sclerosis, unappreciated structural lesions, hereditary disease, and "primary lateral sclerosis".