Cervical myelography (CM) was taken from 14 cases with cervical root-compression symptoms. Prior to myelography, there was complete cranial CT registration to assess the subarachnoid, intraventricular, subcortical and periventricular densities. Control scans at 3,6,24 and 48 h following myelography disclosed intracranial contrast medium at level of basal cisterns, the fourth ventricle and fissura Sylvii. Nine and 11 patients, respectively, had enhancement in the third and lateral ventricles. All patients had subcortical enhancement, and 9 patients had periventricular enhancement; at the 3-h control CT after myelography a minor subcortical edema was disclosed, which declined during the following hours. Two days after myelography, a minimal residual contrast was disclosed subcortically at the level of fissura Sylvii and in the subarachnoid space at the level of fissura Sylvii and the convexity. Hence, we recommend, that diagnostic cranial CT is performed before or postponed until 3 days after cervical myelography. The patients were questioned about adverse effects, and they underwent psychometric assessment and EEG-recordings: 11 had adverse effects, chiefly mild and exclusively transient, without sequelae. Three patients had no side effect. The psychometric assessment, however, disclosed pronounced deterioration in all patients at test 28 h after myelography, especially marked in the verbal paired associates test, however these disturbances were totally absent at retest one week later. No EEG-abnormalities developed; consistently, no patient had seizures. In conclusion, following CM iohexol is taken up by the brain parenchyma, gradually disappearing within 48 h, during which time a brain CT will be disturbed. During the same period some deterioration of psychometric tests may be found.