A reflectometer is described that extends the continuous measurement of the near-normal-incidence reflectance of solids to vacuum ultraviolet (vuv) wavelengths. Clean reflecting surfaces are achieved by in situ sample preparation and ultrahigh vacuum environment. The low intensity problem is solved with electronic lock-in amplification. The over-all instrument has an absolute error of reflectance of (DeltaR/R)(Absolute) = +/-0.03. The precision is estimated to be (DeltaR/R)(Relative) = +/-0.002 or better. The wavelength range of 1100 A to 7000 A is covered. Some representative results show that this design provides substantial improvement in sensitivity and resolution of vuv reflectance measurements.