The elements and organization of an experimental magnetic storage system are described. A rotating wheel is used to give high transfer speeds and relatively short access time to data which are transferred directly to the high-speed cathode-ray tube store of a digital computer. The wheel is run in synchronism with the fundamental frequency of the computer under the control of a servo mechanism. A plated layer of pure nickel is used as the recording medium. A lowimpedance type of head combined with a new method of digital representation have been employed for the storage of data.A complete storage system of this type with a capacity of 3 000 numbers, each of 40 binary digits, has been incorporated in the Manchester University computer.