A gradient in an excess porewater pressure conveys water out of soil during secondary compression. This excess porewater pressure is produced by the tendency of soil to continue compression as a result of the disequilibrium produced during primary compression. Because the measurement of excess porewater pressure is frequently specified for establishing the progress of primary consolidation, it is useful to know the order of magnitude of excess porewater pressure associated with secondary compression. Mathematical analyses and experimental results suggest magnitudes of excess porewater pressure at the beginning of secondary compression corresponding to u′_m/σ′_v=1 to 3 % for C_α/C_c=0.03 to 0.07, respectively, which decrease rapidly with the progress of secondary compression.