Since ossification of posterior longitudinal ligament in cervical spine (O.P.L.L.) was presented at first by Tsukimoto in 1960, many cases have been reported in Japan. But very few cases were reported outside of Japan, including Korea. It is yet unknown what mechanism is the cause and why it is prevalent among the Japanese. And so, there are various theories on the cause. With progression, this lesion cas cause cervical myelopathy and radiculopathy. The treatment of O.P.L.L. is divided into conservative and operative treatment, and the latter is composed of anterior fusion,anterior decompression and posterior decompression. We experienced 3 cases of O.P.L.L. of which two cases were treated by anterior fusion and one tred by anterior decompression with partial removel of ossification mass from March, 1985 to May, 1986. On the follow-up, results were excellent to good. We report our experience in treatment of O.P.L.L. and recommand to be concerned about the lesion.