The authors have investigated the findings of 410 cadavers which were subjected to medicolegal autopsies in our laboratory as to whether their eyelids were open or closed at the time of autopsy and have come to the following conclusions. 1) It has been found that the eyelids of cadavers may open or close spontaneously as a cadaveric phenomenon. In about 27 per cent of cadavers dead from 6 to 12 hours the eyelids were open and thereafter they were closed gradually and all of them were closed from 36 hours to 4 days. After 4 days the eyelids of some cadavers were open again. The mechanism of this cadaveric phenomenon has been discussed. 2) Concerning the opening or closing of the eyelids, neither seasonal variation nor variation by age except newborn infants has been found. In death from exsanguination many were open and in death from drowning and carbon monoxide poisoning all were closed. 3) The findings whether the eyelids of cadavers are closed or open may be utilized as a criterion for estimating the postmortem interval; the cadavers with open eyelids are estimated to have been dead less than 36 hours or over 4 days.