We agree with Jores and others that not one but many factors may be at work leading to intimal hyperplasia. Among these factors may be mentioned infection, bacterial toxins, organic poisons, inflammation and increased arterial tension. The theory of Thoma that the connective tissue developed in the intima is compensatory cannot be sustained. From the evidence which we have at hand it is not possible to state that the proliferative changes in the intima are uniformly secondary to the weakening of the media. Common influences may act simultaneously upon the media and the intima. Progressive medial degeneration of the peripheral arteries (Moenckeberg's sclerosis) is the result of muscle fatigue coupled with nutritional disturbance.