In vertical seismic profiling (VSP) data, large-amplitude borehole Stoneley waves are observed at depths where fractures intersect the borehole. We present a model which predicts the amplitudes of these Stoneley waves as a function of certain parameters of the fractures, namely, the fracture aperture (width), the orientation, and the degree of stiffness and roughness of the fracture. The proposed mechanism for the generation of these borehole Stoneley waves is coupling of a guided mode, induced in the fracture by an incident plane wave (typically a P wave), to the borehole. The model expresses the borehole Stoneley wave amplitude, normalized by the amplitude of the direct P wave, as a function of frequency, in terms of the fracture parameters. The model is used as the basis for an inversion scheme, employing a nonlinear least squares algorithm to estimate the fracture parameters. The inversion is then applied to VSP data where borehole Stoneley waves are observed at depths where fractures are known to intersect the borehole. The results of the inversion indicate that the aperture and vertical component of the orientation (i.e., dip) of the fracture can be accurately estimated but the horizontal component ot the orientation (i.e., strike) is not well resolved. These conclusions are based on comparisons with independent estimates of these parameters from flow tests and borehole televiewer measurements. In addition, stiffness and roughness of the fractures are important effects which must be considered in order to obtain realistic estimates for the other parameters, especially the fracture aperture. ¿ American Geophysical Union 1995