A comparative study of eyelid parameters reported to be important in involutional entropion was made. Males and females aged greater than or equal to 65 years with normal eyelids, acute involutional entropion (history less than 6 weeks), and chronic involutional entropion (history greater than or equal to 6 weeks) were entered into the study. Significant findings were increased vertical laxity in each entropion group and increased horizontal laxity in the chronic entropion group. The upper eyelid action had an essential role in the turning in of affected lower eyelids. The degree of pretarsal overriding in the lower eyelid was not a significant differentiating feature when the groups were compared. The findings of this comparative study provide the basis for suggesting the pathophysiology of involutional entropion.