The technique of open distal anastomosis using deep hypothermic circulatory arrest was used in 69 cases of acute type A aortic dissection. These cases were subcategorized by site of intimal tear, which was found in the ascending aorta in 41 patients (60%), in the arch in 22 patients (32%), and in the descending aorta in 5 patients (7%). Clinical characteristics and complications are described for these subtypes. Hospital mortality, which was 14.5% overall for acute type A dissections, was 14.6% for ascending tears, 18.2% for arch tears, and 0% for descending aortic tears. Six-year survival was 69% +/- 15% for ascending tears, 69% +/- 22% for arch tears, and 80% +/- 25% for descending tears (mean +/- SEM, p = NS). A classification system for aortic dissection is proposed, based on both site of origin and propagation.