A computer program in ANSI Standard FORTRAN 77 language has been developed to simulate waveforms produced by radar altimeters. Single waveforms or trains of waveforms at any pulse interval can be calculated. Antenna characteristics are modelled, including off-nadir pointing. The Earth is modelled as an oblate spheroid upon which any desired topography can be superimposed, either by means of formulae or as numerical data. The angular dependence of scattering coefficients can be treated.