Degrees　of　consolidation　can　be　determined　by　two　different　methods　using　deformation　and　excess　pore　pressure　variations　for　reconstituted　and　natural　clays　in　laboratory　tests　and　engineering　practice.　Theoretically,　the　relationship　between　the　degrees　of　consolidation　determined　using　the　two　methods　should　be　unique.　However,　this　study　finds　the　experimental　results　from　fifteen　one-dimensional　incremental　load　consolidation　tests　on　five　kinds　of　natural　clays　deviated　from　the　theoretical　line.　The　experimental　relationships　correlating　the　degrees　of　consolidation　determined　by　the　two　methods　are　also　found　not　unique,　instead,　consisting　of　a　cluster　of　curves　depending　on　different　step　stress　increments.　Two　key　causes　are　found　to　be　responsible　for　the　substantial　discrepancy　between　experimental　and　theoretical　results:　(1)　the　nonlinear　development　of　deformation　during　the　dissipation　of　excess　pore　pressure;　(2)　the　degree　of　consolidation　determined　by　excess　pore　pressure　measurements　lower　than　100%　when　the　degree　of　consolidation　determined　based　on　the　deformation-time　curve　becomes　100%.　It　is　also　found　that　the　experimental　relationships　correlating　the　degrees　of　consolidation　determined　by　the　two　methods　are　significantly　affected　by　the　values　of　degree　of　consolidation　with　excess　pore　pressure　dissipation　at　100%　of　consolidation　degree　with　deformation　observations.