Bradykinin is one of the most potent naturally occurring substances but little is known of its physiological role and pathological significance in man. The established data are, however, so interesting that they have given rise to many, so far speculative, ideas about its role in disease. As a local chemical control of the blood supply of sweat glands, and as a vasodilator, the substance may be of especial dermatological significance, possibly in respect to the fundamental role of the skin in thermo regulation and to cutaneous disorders which are associated with or modified by disturbances of thermoregulation.