Since the initial work of Hoyer (1), in 1887, and the subsequent investigations of Sucquet (2), Schumaker (3), and others, it has been well demonstrated that there are normal, as well as abnormal, arteriovenous communications in man and in the lower animals. Lewis (4) has shown these normal arteriovenous units, the “glomus bodies” of Masson (5), to be important in the heat-regulatory mechanisms of the body. However, the formation of the peripheral vascular system is not always perfect, and as a result we have the development of a multitude of types of vascular hamartomas, usually of a superficial nature. It is proposed that there are at least three types of congenital arteriovenous communications. 1. The glomus body, a normal physiological arteriovenous communication involved in the mechanism of body heat stabilization, under neuromuscular control. 2. The “central arteriovenous communication,” in which major vessels of either the peripheral vascular bed or the pulmonary circuit are associated. These malformations develop early and probably represent a developmental arrest in the retiform stage of the vascular bed, as described by de Takats (6). This type of arteriovenous communication is large and produces symptoms of a systemic nature which are easily recognized. 3. The “peripheral” or maldeveloped type of glomus unit, as described by Popoff (7), lying in the inner zone of the stratum reticulare and stratum subcutaneum of the skin, is generally deeper than the normal glomus unit. The lumen is large, exceeding 0.1 mm. in diameter, and has little or no neuromuscular control. The potential cross-sectional area of this type of communication is large. Grant and Bland (8) have estimated it to be in excess of 1,209 sq. cm. in the hand, and even more in the foot and leg. An area of pigmentation of the skin may be associated with the distribution of this defect. The diagnosis of central arteriovenous communications, as well as of communications arising on a traumatic basis, is not difficult. The blood flow via such shunts is large, and attention is early directed to them by the usual clinical signs. The third type of arteriovenous communication described above, the maldeveloped glomus unit, presents a much more difficult problem, and in our series of studies is much more common. It is this small type of peripheral arteriovenous communication that will be discussed in this report. Technic of Demonstration Attempts at radiographic demonstration of peripheral arteriovenous communications in the lower extremity were carried out on 8 patients in which such lesions were suspected. The bases for selection were as follows: 1. Abnormal phlebectasia of one extremity. 2. Abnormal skin temperature (elevation) of one extremity. 3. Elevation of the venous oxygen saturation from the femoral vein.