For industrial gas turbines the trend is towards higher efficiency at constant and possibly decreasing costs per kW shaft power. Higher efficiency can be achieved with advanced 3-D aerodynamic design and higher cycle temperatures. To meet the objective of reduced costs it is advantageous to reduce the number of stages resulting in high pressure ratios and transonic conditions for these stages.The demand for efficiency increase and the search for more compactness results in an higher importance of unsteady flow effects. The flow unsteadiness in turbomachinery is highly related to the relative stator-rotor motion and the wakes generated by the cascades of stator blades and rotor blades. Based on the experience gained in the investigation of transonic turbines at the institute, the objective of the proposed project is the investigation of the stator-rotor-stator interaction when the first stage is a transonic turbine stage. This research will result in a detailed study of the influence of the unsteady, transonic flow from a high-pressure stage onto the flow field through a second stator as well as the influence of the second stator onto the preceding flow field.