Eighteen consecutive patients with cerebrospinal fluid (CSF) rhinorrhoea investigated by computed tomographic cisternography (CTC) are reported and the literature is reviewed. Twenty-one CTC studies were performed without complications on nine patients presenting with spontaneous CSF rhinorrhoea, six with head injury and three who had undergone craniotomy. Two meningoceles and two encephaloceles were found in patients with spontaneous rhinorrhoea. The site of the CSF leak was identified in 17 examinations (81%) and verified at operation in 14 patients--no surgery was performed following two examinations--and in one the site of leakage was not identified at operation. No defect was identified in three (14.3%) examinations and in one the result was equivocal (4.7%). CTC is an accurate, well-tolerated procedure and should be regarded as the method of choice for investigation of this condition.