The Tritium Pellet Injector (TPI) is a cryogenic pellet injector which will be used on TFTR prior to and during the D-T phase of operations. The injector will replace the current Deuterium Pellet Injector (DPI) at Bay T with an injection capability for pellets of deuterium and/or tritium or mixtures of both. The gun will be a 4 barrel configuration (replacing the existing 8 barrel system) with one of the barrels capable of high speed. Pellet acceleration will be accomplished pneumatically using high pressure helium and hydrogen gas. The injector has one cylindrical pellet per barrel per shot with each barrel independent of the others. Velocity of the pellets when they are injected into the plasma for the single stage gun will be 1.5 km/sec which is variable from .5 to 1.5 km/sec. For the Two-Stage gun velocities will be 3.0 km/sec. The TPI program is a collaborative effort between Oak Ridge National Laboratories and Princeton Plasma Physics Lab. The TPI program provides a cryogenic tritium pellet injection capability by the Spring of 1993. The project is divided into 2 Phases. Phase 1 which supports deuterium operation and Phase 2 which supports tritium operation. Phase 1 is scheduled for implementation during the Spring of 92 with deuterium operation from April through September of 1992. A very important part of Phase 1 is to verify that the systems required for Phase 2 that are operational will be tested as part of the deuterium effort. Phase 2 is scheduled for implementation and will make the TPI tritium capable by the end of April 1993. ORNL responsibilities include assembly and design of the injector line, development of the injector control system and modification of the gas manifolds. PPPL'S tasks is the system engineering and interface of supporting systems for the operation of the injector during deuterium and also during the tritium phase of operations. This paper will address the mechanical design of the TPI injection facility provided by PPPL with the TFTR machine.