Artificial fractures were created on three different rock samples by sawing. The fracture surfaces were in turn grooved in different directions by sawing to simulate the fracture roughness. Four different roughness types were created and a fracture roughness coefficient (FRC) was defined for each type. Model experiments were carried out on the rock samples having different fracture roughness to investigate how the sound velocity varies with fracture roughness. The test results were statistically analysed using the method of least squares regression and polynomial relationships with high correlation coefficient were found between the FRC values and the P-wave velocities. The P-wave velocity decreases with increasing the FRC values. (C) 2002 Elsevier Science B.V. All rights reserved.