Objectives: Patients (pts) with bicuspid aortic valves (BAV)are at higher risk for aorta-related death (rupture or dissection) than their peers with a tricuspid valve (TAV).Yet it is unclear if BAVs present ata younger age and with a larger root/ascending aorta than their tricuspid peers when suffering acute type A aortic dissection.Methods: 379 consecutive pts with acute type A aortic dissection, transferred to our institution for emergency surgery (11/1995-07/2011) with a median ofl0 (range :< 1-336) hours after symptom onset, were included: 92% with TAV (N=348), 8% with BAV(N=31).Overall, 39% (N=149) of all pts presented with ectasia or root/ascending aneurysm.Results: TAVs presented at a mean age of 62.4±13.3 yrs of age, in contrast BAVs presented significantly youngerat a mean age of48.6±13.8 yrs (N=31, P<.005).63% of all TAVs were male (N=218) vs.71% of all BAVs (N=22).Aortic root / ascending ectasia/aneurysm was present in 52% of BAVs vs.38% of TAVs.An entry tear wasidentified in 95%: in the root/asc aorta in 262 pts (69%), in the transverse arch in 97 pts (26%): in BAVs, the entry tear was located in the root/asc aorta in 83% (N=26) vs.67% (N=236) in TAVs.Overall, 37% (N=139) underwent a composite root replacement: 77% of BAVs (N=24) vs.33% of TAVs (N=115).216 pts (57%) had a supracoronary ascending replacement: BAV: 23%, N=7; TAV: 60%, N=208).The remaining pts had aortic valve / root reconstruction; a total of 67 pts (18%) had an elephant trunk (BAV: 10%; N=3 vs.TAV: 18%, N=64).Hospital mortality for all emergency cases was 19.8 %(N=75): 22 %(N=7) among BAV vs.19.5 %(N=68) among TAV pts.A stroke occurred in 16% (N=60): in 6% (N=2) of BAVs vs.17% (N=58) of TAVs.Conclusions: BAVs dissected at a younger age than their tricuspid peers.In more BAVs, acute type A aortic dissection occurred associated with aortic ectasia/aneurysm.The entry tear was located in the aortic root/ascending more often in BAV mandating complex root surgery.