Canine subaortic stenosis - literature review and own observations According to anatomy aortic stenosis can be classified as supravalvular, valvular and subvalvular. In 95% of examined patients a mild fibromuscular type of SAS was diagnosed, which is the most common CHID. Especially purebred dogs like Boxers, Golden Retrievers, German Shepards, Rottweilers, Newfoundlands and Bullterriers are susceptible for SAS. Since the nineties of the last century an increasing prevalence of this disease has been discribed on Boxers in Great Britain, France and Italy, furthermore it's known for Golden Retrievers in Canada. Breeder associations in Great Britain have kept records of several deaths of juvenil Boxers in the end of the eighties. Based on the cases of sudden death, systematic examinations (auscultation and ultrasound examinations) have been enforced in the Boxer breed, resulting in the exclusion from the breeding of individual dogs. The aim of this article is to give a detailled survey of embryology, anatomy, pathophysiology, clinical symptoms, prognosis, diagnosis, screening methods and therapy of SAS. Additionally we compare some parameters taken from a retrospective study on the appearance of SAS in patients examined at our clinic (1996-2003) with data found in the world litarature. In the most reports as well as in our patients SAS is the most common heart disease. In Newfoundlands hereditary transmission has already been proven whereas in other breeds it is assumed. Due to typical pathomorphological changes we normally differentiate 3 stages, though some publications also describe atypical forms. A very sensitive method for diagnosis is echocardiography, in particular doppler sonography. The measured aortic blood flow velocity is used to quantify the disease by applying certain velocity intervals for different breeds, but unfortunately some cases stay inconclusive. Most dogs with SAS only have a mild form with an associated heart murmur as the only clinical finding. Whilst the mild form is difficult to diagnose the severe form on the other hand is difficult to treat. Most authors suggest beta-blocker therapy in moderate to severe diseases.