We discovered a pressure-induced metal-insulator transition in Ti4O7 which is a bipolaronic insulator at ambient pressure. In the pressure-induced metallic phase, the resistivity shows T2-behavior at low temperatures. From the remarkably large magnitude of T2-resistivity and its pressure dependence, we suggest that electron correlations are very likely the primal origin of the bipolaronic insulator phase of Ti4O7. In spite of early expectations, superconductivity was not observed down to 3 K.[metal-insulator transition, electron correlation, Mott transition, T2-dependent resistivity, bipolaron]. © 1998, The Japan Society of High Pressure Science and Technology. All rights reserved.