SUMMARY A directional borehole antenna has been developed for the RAMAC borehole radar system. Several methods previously used to locate fracture zones in rock are reviewed. In comparison with these methods of analysing radar data the directional antenna makes it possible to obtain the position of a reflector by measuring in a single borehole. The antenna has been successfully tested in the Stripa mine in connection with the characterization and validation program presently in progress. From the measured signals the antenna synthesizes the directional field in an arbitrary direction as well as an electric dipole field which can be used for phase comparison. The function of the antenna can also be checked during measurements. Methods for extracting the directional information are described and exemplified. The angular resolution is f5" in favorable cases.