A simple method has been developed for estimating wave height from synthetic aperture radar 7lpar;SAR) imagery obtained by the Seasat satellite. The method is based on measuring the contrast of the image and the wavelength of the dominant wave. A calculation has been made for two orbits made by the satellite over the North Atlantic in 1978, using digitally processed data supplied by DFVLR in West Germany. Comparison with sea truth measurements shows agreement to within about 20 per cent.