Breed predispositions for some types of congenital heart disease were recognized 30 years ago and led to breeding experiments that confirmed the genetic transmission of specific congenital heart defects in most instances. As a result, certain breeds were associated with certain diseases, and this became a legitimate consideration in the differential diagnosis of some abnormalities in the absence of more definite diagnostic studies. As an example, a significant systolic murmur in a young Newfoundland dog means sub-aortic stenosis (SAS) until proven otherwise. The diagnosis of SAS is usually confirmed by Doppler echocardiography or angiocardiography. Although cardiologists take breed into consideration, they still rely on proper examination and appropriate diagnostic procedures; however, practitioners are comes pressed to give opinions on the likelihood of particular diagnoses and prognoses without benefit of a full work-up. In this setting, knowledge of new and changing breed predispositions can be helpful. In recent years, some defects and new breeds have been found to be overrepresented in cardiology clinics across the country. All practitioners need to be alert in order to recognize new breed predispositions and counsel breeders accordingly. Of particular note is the rising frequency of SAS in Golden Retriever and Rottweiler dogs. The purpose of this presentation is to describe changing breed predispositions that have been observed in recent years and share the results of a recent tabulation of data at our institution as well as 1987- 1989 data in the national Veterinary Medical Data Base (VMDB) at Purdue University.