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Ground-penetrating radar (GPR) was used to locate fractures and distinguish fracture properties at the laboratory and field scales. Laboratory studies were performed to define the effects of fractures on the GPR signal. In the laboratory, a fracture between two blocks of crystalline rock was filled with water or air, and the aperture of the fracture was varied from 0.75 to 10 cm. Air-filled and water-filled fractures were successfully distinguished on the basis of GPR signal polarity changes. Moreover, it was possible to estimate the fracture aperture when it was wider than the vertical resolution of the antenna. For instance, the resolution of a 800-MHz antenna enables the detection of 1-cm-wide water-filled openings. Armed with knowledge of the signal behavior at the laboratory scale, the apertures and the filling materials of fractures were also estimated in uncontrolled field conditions. These field studies were carried out in a dimension stone quarry of migmatitic granodiorite located in Southern Finland. [ABSTRACT FROM AUTHOR]