The results of surgical repair of patent ductus arteriosus (100 dogs) were compared with the results of nonsurgical treatment of this defect (14 dogs). The death rate for dogs surgically treated was 8%, with 2 deaths at surgery and 6 late postoperative deaths. In the nonsurgical group, 64% died within one year of the examination. The increased survival rate for the surgically treated group was significant ( P less than 0.001). Surgical death rate was high for dogs more than 2 years old and weighing more than 23 kg. It was concluded that surgery is the preferred method of treatment and that early surgery increases the survival rate of dogs with patent ductus arteriosus, compared with the survival rate for older, heavier dogs with the defect.