Magnetostriction and magnetoresistance of single-crystalline HoNi 2 B 2 C have been measured at ambient pressure. A large anisotropy was found in the field dependence of these properties. The magnetoresistance was also measured at high pressure up to 2GPa at low temperature below the superconducting transition temperature (9K). Several anomalies were found due to the metamagnetic transitions, in which the transition fields increased with increasing pressure. These results will be discussed from a thermodynamical point of view and compared with the anisotropy in the lattice compression.