THE PURPOSE of this paper is to present a classification of congenital ptosis illustrating its diverse and complicated nature. Such a presentation is desirable because the operative results of congenital ptosis, in the hands of experienced surgeons, depend on two conditions: (1) the nature of the ptosis present and (2) the type of operation selected. This study, therefore, is designed to simplify the classification of congenital ptosis and to assist the surgeon in selecting the proper procedure for each type of ptosis. This classification of ptosis is based on a personal survey of the hospital records of 200 consecutive cases of ptosis seen at the Institute of Ophthalmology, Presbyterian Hospital of New York City, during the past fifteen years. The original preoperative observations were made by various members of the attending and resident staffs. In all cases the vision was recorded for each eye, when possible; the vertical widths, and