Examination of liver alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) isozymes together with the estimation of alcohol in the body fluids of the deceased, may help to estimate more accurately the grade of their drunkenness. However, in medico-legal cases the body is sometimes putrefied or burnt. In the present study, the effects of putrefaction and heat on the activities of human liver ADH and ALDH isozymes were investigated by thin layer polyacrylamide gel isoelectric focusing. When the liver homogenates were left at 5℃, identification of typical type and atypical type of ADH became impossible within 10 days and 6 days, respectively. In some of the homogenates left at the same terperature, the activity of normal type and deficient type of ALDH2 isozyme was detected for 21 days. When the homogenates were stored at 25℃, the activities of the ADH and ALDH disappeared within 2 days and 3 days, respectively. Identification of ADH typical type, ADH atypical type, ALDH2 normal type and ALDH2 deficient type of the homogenates stored at 37℃ became impossible within 12 hours, 3 hours, 24 hours and 21 hours, respectively. These results indicate that the activity of the ADH disappears faster than that of the ALDH at room temperature and that atypical type of ADH is more sensitive to putrefaction than its typical type. The same phenomena were also observed in liver of decomposed corpses. When liver homogenates were stored at 50℃, it was possible to identify the type of ADH for about 5 hours. In the homogenates stored at the same temperature, the activity of the ALDH2 isozyme disappeared within about 1 hour though the ALDH1 isozyme was stable for 5-6 hours. The activities of ADH and ALDH of the homogenates quickly disappeared when heated at 70℃ and 100℃. In burnt bodies whose liver almost remained intact, the activities of the ADH and ALDH enzymes did not decrease though they were badly charred. However, only the ALDH2 band disappeared in some parts of the liver burnt slightly though the ALDH1 band was visible. In such a burnt body, therefore, it is necessary to examine the ALDH isozymes of the liver and kidney not to misjudge ALDH2 normal type as ALDH2 deficient type. Ten human corpses, which were of alcohol-consumers, all showed normal type of ALDH2 isozymes. The frequency of ALDH2 deficiency was about 21% in our medico-legal autopsy cases though it is about 50% among the Japnese.