The motion of [10 (1) over bar 0]/theta ice grain boundaries is studied using the "Sun-Bauer" technique. The samples were annealed at temperatures between -2 degrees C and -20 degrees C, for times up to 1400 h, and M gamma values for mixed and tilt boundaries were determined (M and gamma are the mobility and the excess of free energy per unit area of the grain boundary, respectively). For each rotation angle theta and annealing temperature, a large scattering is found in M gamma values. This scattering is related to the dependence of migration on grain boundary inclination. The obtained results are specially analyzed taking into account CSL concepts and grain boundary migration in anisotropic materials.