This investigation has been carried out to determine experimentally the influence of the thermal resistances of the tube wall and the heating medium (inside flow) on the critical heat flux over a cylinder of large diameter placed horizontally in a cross flow. The cross flow was normal to earth gravity. The parameters varied were the tube material, tube thickness, flow rate of heating medium, undisturbed cross velocity of the coolant and coolant subcooling. The experimental results are discussed and a qualitative explanation for the experimental findings is given.