Al2O3–B4C composites containing up to 40 vol.% of dispersed B4C particles were fabricated by hot-pressing and machined as cutting tools. This composite showed higher micro-hardness and toughness than monolithic Al2O3 because of the restricted grain growth by the presence of hard B4C particles. Machining tests were conducted on a carbon steel work piece to evaluate the performance of the Al2O3–B4C cutting tool.