Idiopathic trigeminal sensory neuropathy is a rare disorder characterized by transient sensory disturbances in the territory of one or more branches of the trigeminal nerve. Acute and chronic forms of the disease have been recognized, but the boundaries between these groups are not clearly defined. Six cases of idiopathic trigeminal sensory neuropathy are reported. All patients presented with sensory abnormalities limited to the territory of one trigeminal nerve, in the absence of other clinical features. The symptoms were on the left side of the face in five cases and on the right side in one. No bilateral involvement was seen. There were no cases of muscle weakness, and the corneal reflex was always present. In two cases, sensory disturbances began in the tongue or lips and later spread through the entire territory of the three trigeminal branches. Both patients recovered completely after 3 months. The other four patients had involvement of the second and third branches (two cases), or the third branch alone (two cases), and the symptoms persisted unmodified for 2 to 4 years. There were no clinical variables at onset to enable one to predict an acute or chronic evolution of the disease.