The high pressure turbine stage can be considered the most important component for the efficiency and longevity of a modern gas turbine. The flow field within this stage is highly complex and is both unsteady and three-dimensional. Understanding this flow field is essential if improvements are to be made to future engine designs. Increasingly designers are placing more emphasis on the use of Computational Fluid Dynamics (CFD) rather than experimental results. CFD methods can be more flexible and cost effective. However before these predictions can be used they must be validated against experimental data at engine conditions. The hostile environment and complexity of flows within a gas turbine engine mean that collection of experimental data is extremely challenging. This thesis describes the development of an instrumentation technique for unsteady gas turbine flow measurement capable of resolving unsteady three-dimensional flow. The technique is based on an aerodynamic probe constructed with miniature semiconductor pressure transducers manufactured by Kulite Semiconductor Inc. Measurements recorded using this instrumentation technique from the Oxford Rotor experiment are presented to illustrate its use, and these in turn are compared with a CFD prediction of the rotor flow-field. This work was funded by the Engineering and Physical Sciences Research Council and Kulite Semiconductor Inc. The Oxford Rotor project is jointly funded by the Engineering and Physical Sciences Research Council (EPSRC), and Rolls-Royce Plc.