A case of carotid-cavernous fistula following percutaneous trigeminal ganglion approach is presented. The case was treated by a combination of trapping and embolisation of the carotid artery. Percutaneous approach to the trigeminal ganglion via the foramen ovale was described by Taptas (1911) and Hartel (1914). Since then this procedure has been used in large series, for the injection of alcohol (Harris, 1940), electrocoagulation (Kirschner, 1942) or the injection hot water (Jeager, 1957) to the trigeminal ganglion for the treatment of trigeminal neuralgia. In 1965 White and Sweet used the percutaneous trigeminal ganglion approach for the radio-frequency (R.F.) thermocoagulation of the trigeminal ganglion. This procedure is a simple and safe method. It has been used in large series in the treatment of trigeminal neuralgia. In our department we have performed 252 R.F. thermocoagulation of the gasserion ganglion in 228 patients since 1975. In 252 interventions using the percutaneous trigeminal ganglion approach, via the foramen ovale, we observed only one carotid-cavernous fistula following the procedure. This is the second report in the literature of a carotid-cavernous fistula following the percutaneous trigeminal ganglion approach.