Three‐dimensional finite element (FE) wave propagation models have been used to examine the effect of defect geometry and frequency on the reflection coefficients of longitudinal guided waves in 3″ Schedule 40 steel pipe. An insight into the propagation characteristics of guided waves in rails is also presented. The dispersion curves for a rail are discussed and modelling results of the variation of reflection coefficient with defect depth is presented for a BS113A type rail. © 2003 American Institute of Physics