Summary C.S.F. Rhinorrhoea must not be considered only in conjunction with fronto-basal fractures. If the patient's history provides no indication of a traumatic cause, various intracranial and extracranial changes must be taken into consideration and a comprehensive diagnostic investigation of the base of the skull instituted. C.S.F. Rhinorrhoea may also be caused by fractures of the posterior and middle fossae of the skull. Possible forensic difficulties should be taken into consideration by carrying out a complete diagnostic investigation at the earliest possible time and involving all the appropriate specialities.