For the last sixty years many have studied the histologic changes in the smaller arteries in diffuse disease of the vascular system. There has been considerable controversy as to whether any characteristic pathologic lesion is present. Our interest in this subject was renewed when the ophthalmologist was so frequently able to demonstrate narrowing of the retinal arteries and arterioles in cases of malignant hypertension. A year ago Keith, Wagener and Kernohan1 were able to show in such a case that there were common features in the smaller arteries and arterioles in many organs, including those supplying the voluntary muscle. The latter observation suggested that biopsy material from a superficial muscle in ambulatory cases of hypertension might show early histologic changes in the smaller arteries. Muscle tissue was chosen because it composes about 35 to 40 per cent of the body and thus an assumption that there is a widespread lesion