Incremental　load　one-dimensional　consolidation　tests　were　performed　on　undisturbed　and　reconstituted　specimens　of　seven　natural　clays　with　a　predominant　clay　mineral　of　illite.　Both　the　settlement　and　the　base　pore　pressure　under　step　load　increments　were　measured　during　the　dissipation　of　pore　pressure.　The　change　law　in　the　primary　consolidation　time　determined　by　the　pore　pressure　dissipation　with　increasing　stress　level　is　found　to　be　contrary　to　that　determined　by　the　Taylor　method　and　the　Casagrande　method　which　are　often　used　in　laboratory　tests　and　engineering　practice.　The　primary　consolidation　time　determined　based　on　the　time-dependent　settlement　observations　is　smaller　than　that　determined　by　the　pore　pressure　dissipation　for　the　natural　clays　investigated.　Pore　pressure　is　generally　not　completely　dissipated　at　the　primary　consolidation　time　determined　by　the　Taylor　method　and　the　Casagrande　method.　Such　remaining　pore　pressure　may　reach　a　quite　high　percentage　of　the　step　load　increment　for　the　investigated　specimens.　The　settlement　determined　by　the　Taylor　method　and　the　Casagrande　method　may　be　significantly　underestimated　due　to　the　dissipation　of　remaining　pore　pressure.　Attention　should　be　paid　to　the　possible　distortion　on　consolidation　behavior　in　laboratory　tests　and　engineering　practice　due　to　the　remaining　pore　pressure　and　the　associated　settlement.　©　2015　Elsevier　B.V.