By combining the time-of-flight or LIDAR principle with a Thomson backscatter diagnostic, spatial profiles of the electron temperature and density can be measured with a single set of detectors for all spatial points. This approach considerably simplifies the collection optics required for measuring a spatial profile. The technique was realised for the first time on the JET tokamak and has been in routine operation since July 1987. A ruby laser (3J pulse energy, 300ps pulse duration, 0.5Hz repetition rate) together with a 700MHz bandwidth detection and registration system yields a spatial resolution of about 12cm. A large filter spectro meter with 6 spectral channels covering the wavelength range 400–800nm gives a dynamic range of the temperature measurements of 0.3-20keV. The stray light problem in the backscatter geometry is overcome by spectral discrimination and effective gating of the MCP photomultipliers. A high rejection ruby notch filter in the spectral channel contain ing the laser wavelength allows calibration of the vignetting along the line of sight by means of Raman scattering, thus enabling the measurement of density profiles. The low level of plasma background signal due to the short integration time for an individual spatial point yields low statistical errors (ΔTe/Te ≈ 6%, Δne/ne ≈ 4% at Te = 6keV, ne = 3×1019 m–3). Goodness-of-fit tests indicate that the systematic errors are within the same limits . The system is described and examples of measurements are given and compared with the results of other diagnostics.