Isolated hypoglossal nerve paresis as a manifestation of Behcet's disease has not been reported. We describe a 42-year-old man with isolated unilateral hypoglossal nerve paresis, who had had a five-year history of recurrent orogenital aphthae and relapsing arthritic manifestations. It is suggested that the nerve disorder represents a form of mononeuritis that may occur in Behcet's disease.