Thirteen cases of syringomyelia which was confirmed by metrizamide CT myelography (MCTM) were reported. Nine cases were associated with Chiari malformation, and four were idiopathic type. Delayed CTM which were performed in several hours after the metrizamide myelography disclosed not only the existence of the syrinx but its shape and location. From the investigation of their clinical findings together with the appearance of their syrinx on CT scan, the following results were obtained. The syrinx was not always situated centrally within the cord, but had laterality at some spinal level in nine out of thirteen cases. The main laterality of the syrinx seemed to be located in the posterior horn. In the cases which had unilateral dissociated sensory disturbance, the laterality of sensory disturbance corresponded with the side of syrinx. These results suggested the possibility that the intrathecal injected contrast materials entered into the syrinx via the dorsolateral sulcus of the cord rather than via IV ventricle in some cases.