THE term “craniostenosis,” or “contraction of the skull,” in its general meaning is applied to all conditions where a disproportion exists between the size of the skull and its contents. This is found, for example, with tumors of the brain or meninges and with hydrocephalus. In the more restricted sense, however, the name “craniostenosis” is applied only to those anomalies which lead to a diminution in the actual size of the skull cavity. Such a contraction is caused most commonly by premature closure of the sutures of the skull. Normally, the obliteration of these sutures does not occur until the later decades of life, therefore, every closure of these sutures in the earlier decades must be considered as premature. Suture closure is of practical significance, however, only when it takes place during intra-uterine life, or in the first year of post-fetal life. During this period the growth of the skull is possible on account of the suture spaces. Later the skull develops only by periosteal apposition and resorption, just as in the basal synchondroses. Premature synostosis of the sutures is to be regarded as a congenital malformation, which may often occur hereditarily. The earlier the synostosis takes place, and the greater the number of sutures involved, just so much more marked is the degree of skull contraction. When all the sutures are closed the skull remains so small that it resembles a microcephalic skull. The closure of only single sutures may often cause no contraction at all, since those which remain open take on a compensatory function. This compensation is seen externally in the irregular development of the skull in various directions. The nomenclature of the different types of craniostenosis is based upon the character of the skull deformity. This, in turn, is determined by the relative importance of the elements of contraction or compensation. Thus we have “tower skull” (oxycephaly), “boat skull” (scaphocephaly) , “flat skull” (plagiecephaly), “pseudo-microcephaly,” etc. The clinical symptoms of craniostenosis are dependent upon two factors: (1) the deformity, and (2) the contraction of the skull. The latter causes headache, papilledema, epileptoid attacks, psychic disturbances, etc., just as would any other kind of disproportion between the size of the skull and its contents. As for the deformity itself, there are, first of all, very definite esthetic and cosmetic disadvantages for the patient (Schüller). The abnormal height or the abnormally small size of the skull are in themselves disfiguring. The unfavorable impression which these patients make upon an observer is further increased by their having a forehead which is either steep, protrudes too much, or recedes abnormally. The base of the nose may project, the nose itself may be too large, the eyes may be either too close together or too far apart, may protrude markedly, or may have a bad squint.