Potato starch-water mixtures (10 to 70 % w/w) were treated with high hydrostatic pressure (HHP) up to 1.2 GPa, and then gelatinization and retrogradation properties were investigated by differential scanning calorimetry (DSC). DSC thermograms for HHP-treated samples showed various characteristic thermal behaviors depending on the treatment pressure and starch content, and enthalpy changes for gelatinization (ΔH_gel) and regelatinization of retrograded starch (ΔH_retro) of each HHP-treated mixture were evaluated. From the changes of ΔH_gel and ΔH_retro, the physically modified states of HHP-treated potato starch-water mixtures were classified as follows: no change, partial gelatinization, complete gelatinization, partial gelatinization and retrogradation, and complete gelatinization and retrogradation.