There is a limited understanding of the pathogenesis of dolichoectatic (dolicho = long; ectatic = dilated) aneurysms of elastic arteries. Therefore, we developed a model of dolichoectatic changes in elastic arteries by injecting porcine elastase into the media of the carotid artery of male New Zealand white rabbits. After 3 months, gross examination of the carotid arteries in vivo revealed dilated and tortuous vessels. The carotid arteries were then harvested, and cross-sections of the vessels were stained by the Verhoff-van Giesson stain. Histologically, the internal elastic lamina was dissolved in the most dilated areas. The elastic lamellae of the media were also digested and there was reorientation of the innermost medial smooth muscle layer. These gross and histologic changes were present in 80% of the treated carotid arteries and in none of the contralateral control vessels. Our study suggests the importance of the elastic lamellae for the maintenance of tubular shape and length of the carotid artery and describes a new chronic animal model of dolichoectatic aneurysm of the common carotid artery.