The muscle of rudder fish (one of the deep-sea fishes, Centrolophus niger: Stromateidae) contained a large amount of lipid which showed an extremely higher value for unsaponifiable matter contents and lower saponification value than of other fishes. Moreover the lipid showed very low triglyceride contents. The trimethylsilyl derivatives of unsaponifiable matters were analyzed by the methods of gas-liquid chromatography and mass spectrometry. These results assured that the unsaponifiable matters had the 1, 2-diol structure, and were presumed to be glyceryl ethers. We also investigated about the muscle lipids of some deep-sea fishes (silver king fish: Rexea solandri, silver fish: Sriollela punctata, Black cod: Anopiopoma fimbria). The triglyceride was the major constituent of their muscle lipids. Among them, silver king fish had the lowest saponification value and the highest contents for unsaponifiable matters which showed the same properties as that of rudder fish.