It is well known that a great many diseases show a marked sex predisposition. This is true not only of the ailments of adults but of those of children. Thus, pyloric stenosis is from five to six times as common in boys as in girls. Chorea is more than twice as frequent in girls as in boys. Congenital laryngeal stridor is said to be more common in males. 1 Such knowledge is often of diagnostic and prognostic value. It has, however, another significance: when environmental conditions for the two sexes are uniform, it indicates, in infants at any rate, a constitutional predisposition for the particular disease, which may be an aid in evaluating the factors that determine its occurrence. The relationship of sex to infantile tetany has received little attention in the literature. Most textbooks and monographs do not mention the subject. Griffith 2 states that the condition is more