IN THE compilation from the literature by Harris, Lynch and O'Hare,1 hypertension was found in two thirds of the reported cases of periarteritis nodosa. In the large single series of 29 cases reported by Ralston and Kvale,2 there was hypertension in 20, and in five of these cases the condition was considered to be primary hypertension. Elevation of blood pressure is known to develop fairly frequently during the course of periarteritis nodosa. For this reason the hypertension of periarteritis nodosa is usually thought to be secondary in character. Hypertension, often asymptomatic and of unknown origin, occurs with sufficient frequency in the general adult population to account for the occasional chance development of periarteritis nodosa in a person whose blood pressure is already elevated. There is, however, some evidence to suggest that elevation of blood pressure may predispose to the development of periarteritis in certain susceptible persons.