The authors report two cases of Teflon-induced granuloma occurring as a result of microvascular decompression using Teflon wool for the treatment of trigeminal neuralgia (TN). Teflon, which is used to separate a compressing vessel from the root entry zone (REZ) of the trigeminal nerve at the brainstem, is presumed to be an inert material. In the two cases reported here, however, Teflon induced a foreign body reaction at the REZ, causing recurrence of TN. The patients' pain was cured by complete decompression or partial sensory rhizotomy of the trigeminal sensory root at reoperation. Teflon-induced granuloma has occurred in 1.3% of the authors' series of 155 patients with TN treated using microvascular decompression. Recommendations for avoiding this complication are offered.