Congenital total hemihypertrophy, characterized as the name implies, by symmetrical enlargement or hypertrophy of the whole side of the body, is one of the rarest anomalies known to medicine. Its rarity can be appreciated by the fact that, in a complete survey of the literature on this subject, but forty-one cases of true hemihypertrophy could be collected. An example of this curious anomaly of development came under our observation recently, and it is because of its rarity and interest that we wish to report it here, with a brief review of the literature. REPORT OF CASE History. —A. P., a white girl, aged 16, admitted to the service of Dr. Stanton at the Passavant Hospital, June 12, 1921, complained of a small tumor in the left breast which she had noticed for a month previously. In the course of a routine physical examination, it was noticed that the entire left