The clinical presentation and radiological features were analyzed in 30 cases of syringomyelia associated with Chiari malformation. None of the patients had spinal dysraphism. The age on admission ranged from 6 to 59 years with a mean of 27 years. Syringomyelia was diagnosed by CT myelography and or MRI from 1982 to 1988. The initial symptoms were skeletal abnormality (43%) such as scoliosis (12 cases) or pes cavus (one case), unilateral pain or numbness (40%) and unilateral motor weakness (17%). Frequently seen signs on admission were sensory deficit (100%), scoliosis (57%), muscle weakness (57%), muscle atrophy (37%) and lower cranial nerve palsy (40%). The neurological findings were asymmetrical in all patients. The characteristic neurological findings in the cases presenting under 20 years of age were unilateral sensory and motor deficits (61%) with decreased or absent deep tendon reflex on the same side. The localization of the syrinx in axial section varied according to the level even in the same case. In 15 cases with unilateral sensory disturbance or unilateral sensory and motor deficit, the syrinx was located in the region corresponding to the posterolateral portion on the same side as that of sensory disturbance in the cervical or thoracic level. On the other hand, in 15 cases with bilateral sensory and motor deficit, the syrinx was located in the central portion and extended into the posterolateral portion of the more affected side.(ABSTRACT TRUNCATED AT 250 WORDS)