An inversion procedure is formulated based on the modification of the theory proposed by Brown and Scholz (1985) and has been successfully tested with synthetic and laboratory data. The inversion finds average height z¿, standard deviation &sgr;, and average aperture. These three parameters characterize the surface roughness and aperture of a fracture. The inversion results agree with the profile measurements quite well. ¿American Geophysical Union 1992