New glutaraldehyde-treated vascular prosthesis tubes of bovine pericardium were placed in the abdominal aortas of 29 mongrel dogs and observed for 30 to 540 days. Clinical evaluation was performed during follow-up, and histologic and arteriographic studies were done at the end of the study. Patency was shown by arteriography in 27 of 29 tubes (93.1%). Neoendothelialization was found in all grafts, and there was a mixed effect, characterized by both rejection and foreign body reaction in the prostheses from 180 days onward. Both the handling and consistency of the grafts were excellent for implantation. Graft procoagulation and animal anticoagulation were not necessary.