SummaryPost-traumatic and post-arachnoiditic syringomyelia is described in 31 patients from the Midland Centre for Neurosurgery and Neurology (MCNN). It is suggested that the mechanisms may be similar in the two groups and that treatment is best directed to disabling the likely filling mechanisms by opening up the cerebrospinal fluid (CSF) pathways and deliberately leaving the dura open to create an artificial meningocele. It is suggested that drainage on its own is inappropriate but that when drainage of the syrinx is chosen as an ancillary technique then syringopleural drainage may be the procedure of choice. Key words: Spinal cord injuries; Syringomyelia; Arachnoiditis; Post-traumatic cystic myelopathy.Since the presentation of 10 cases of post-traumatic syringomyelia to the IMSOP (Williams et al., 1981) further cases have been seen. The majority of these have been cases with complete or partial paraplegia. Because of the important similarities, the blockage of the CSF pathways around the cord, the upward extension of the syrinx cavities, particularly in association with straining and the tendency to progress, sometimes many years after the causative lesions, it seems probable that the mechanism of the syringomyelia is often similar in both the post-traumatic and the post-inflammatory types of case. The main difference between them seems to be that in some of the post-traumatic cases the condition becomes evident early, only a few months after the initial cord involvement. This may be a manifestation of a supposed haematoma at the site of injury. This possibility is largely unexplored at present and it is therefore not possible to separate the cases retrospectively. Thirty one cases are presented with 7 of them being non-traumatic and the principles of treatment discussed for both types together. Initial results of treatment have been disappointing and have lead to emphasis in surgical management being placed on prevention of the filling mechanisms and the replacement of syringo subarachnoid shunting by more forceful methods of drainage using shunting from syrinx to extrathecal sites, the pleural cavity being chosen in the more recent cases