A retrospective appraisal of traditional neuroradiological techniques (such as direct röntgenograms, cerebral angiography RISA-cisternography, and pneumo-cisterno-encephalography, as opposed to the "new" technique of computer-assisted tomography) was carried out in a series of 82 cases of opto-chiasmatic arachnoiditis, all surgically verified. It is concluded that none of these examinations can provide a reliable diagnosis of opto-chiasmatic arachnoiditis, which preoperatively can only be a tentative diagnosis that becomes final only when confirmed by surgical findings. In the presence of certain progressive neuro-ophthalmological symptoms and signs, a negative neuro-radiological investigation should not deter the neurosurgeon from exploring the chiasmatic region. Computer-assisted tomography, of which the authors have no personal experience in these cases, may hold the future answer to the diagnostic problem.