A simple fixed frequency microwave reflectometer installed on the JET tokamak device is described. Data from the reflectometer are combined with data from other JET diagnostics to obtain the radial distribution of the electron density during the rise and decay phases of the plasma. The profiles are compared with those obtained using a conventional multichord transmission interferometer, and good agreement is obtained. The reflectometer is used to study movements of particular density layers due to MHD and sawtooth activity during the equilibrium phase of the plasma. The limitations of the device are discussed and some possible future developments outlined.