During 8 months, three consecutive cases of syringomyelia were treated by the placement of thecoperitoneal shunts. In the first two patients, the cord cavitation was idiopathic in one and thought to be related to spinal trauma in the other. In the third case, there was associated anomaly of the craniocervical junction of the Chiari I type. Surgery was followed by clinical improvement in all patients. Postoperative magnetic resonance images showed definite diminution of the syringomyelic cavity. The results of treatment seem to support the use of the technique as a primary treatment of syringomyelia associated with progressive myelopathy.