A new non-destructive pipe inspection method, ultrasonic guided wave method as well as the comparison between ultrasonics and guided waves is introduced. An investigation of the guided ultrasonic waves traveling along pipes with fluid loading on the inside and outside of the pipe is described. The effect of inner and outer media has been researched by considering a steel pipe with air and water inside and outside the experimental pipe. Site experiment was carried out on a heating pipe in the resident area of Bohai Oil Company, China. A typical cylindrical guided wave, longitudinal guided wave was used to examine pipes with artificial defects and its propagation characteristics along the pipe were studied. Good agreement has been obtained between the experiments and predictions for pipes with different loading on the pipe.Copyright © 2006 by ASME