Finite element analysis calculations are performed to determine the temperature profile in sections of the ITER Electron Cyclotron Heating (ECH) transmission line waveguide.  Each aluminum, corrugated waveguide transmission line will transmit up to 1.5 MW of electromagnetic radiation over roughly 200 meters from a 170 GHz gyrotron to heat the plasma in the tokamak.  The “ridged tube” waveguide has integral water cooling traces which are lined with copper tubing.  Each transmission line includes miter bends which may be actively cooled and waveguide couplings, where the waveguide cannot be actively cooled due to coupling hardware.  The amount of cooling water available is limited, so determining the required amount of water in the cooling lines is essential.  Finite element computational analyses are performed to determine the effect of the heat load and water cooling on the temperature profile of the waveguide in various steady-state cases.