Ifenprodil, NMDA receptor antagonist, was very effective in the treatment of 3 patients with severe trigeminal neuralgia. Patient 1：A 70-year-old female had been treated for macroglobulinemia in our hospital. She had been suffered from severe trigeminal neuralgia for more than ten years. Carbamazepine given in another hospital was ineffective. We gave ifenprodil to her and it reduced her pain within 4 weeks. However, her pain relapsed after 1.5 years, so we gave pregabalin instead of ifenprodil to her. Patient 2：A 89-year-old male had been treated for myelodysplastic syndrome in our hospital. He also had been treated for trigeminal neuralgia in another hospital. Carbamazepine was ineffective and nerve block relieved his pain temporarily. We gave ifenprodil to him and it reduced his pain within 2 months. Patient 3：A 62-year-old female was referred to our hospital for the treatment of trigeminal neuralgia. She had been suffered from severe pain for about 10 years. She had taken carbamazepine with no effect. We gave ifenprodil to her and it reduced her pain within 4 weeks. Ketamin, non-selective NMDA receptor antagonist, is known to be effective in neuropathic pain, but it has various side effects. Ifenprodil, specific NMDA receptor subunit NR2B antagonist, may show better separation between efficacy and side effects.