[en] Metrizamide CT (M-CT), as well as metrizamide myelography (M-M), has been used frequently as a means of providing diagnostic information for spine surgery. Causes of false negative (FN) and false positive (FP) M-CT images were examined with the findings of other imaging modalities and surgery. FN images occurred (1) in lesions that are difficult to detect on the existing scanner, including intradural arachnoid deverticulum, tight filum terminale, and syringomyelia; and (2) in cervical myelopathy and herniation of intervertebral disk, in which the compression on the spinal cord sometimes decreases or disappears by the patient's position at scanning. FP images occurred (1) when metrizamide entered the epidural space or the space between the dura and arachnoid; and (2) when the dosage was too large. M-CT is of limited value in diagnosing some diseases of the spine or spinal cord. It is recommended to scan the cervical area in prone position and to combine M-CT and M-M in routine practices. (Namekawa, K.)