A general method for predicting the lifetime of a polyethylene structure that fails by slow crack growth was applied to the case of externally notched pressurized pipes. An analysis of experimental data indicated that the residual stress must be taken into account. The critical notch depths associated with a given lifetime were calculated as a function of pipe size, PENT value of the resin, and temperature. The results were tabulated to serve as practical guide lines for deciding whether a pipe should be discarded if the notch is too deep. The current 10% of the thickness rule now used by industry was found to be invalid.