The results of the use of the methylglucamine salt of the iothalamic acid (MGI) for ventriculography in 54 patients is reported. The technique for serial ventriculography is described being emphasized the high diagnostic quality of x-ray pictures as well the absence of toxic or irritative effects after the use of MGI. This water-soluble contrast has been extremelly helpfull as a diagnostic aid for localizing supra and infratentorial midline lesions as well for III ventricle tracings during stereotaxic surgery.