Abstract: A method for estimating pore fluid pressures in subterranean formations is disclosed for use in evaluating potential problems that might be encountered in drilling wells. It is a mathematical method based on the assumption that the second derivatives of an interval velocity vs. depth relationship, whether obtained by seismic means or from well sonic information, are equal to the second derivatives of the effective vertical stress relationships in the formations described by the interval velocity relationship. The assumption, and thus the method, is thought to be entirely general except in the presence of formations heavily saturated with natural gas.