A heart murmur is caused by turbulent blood flow within the heart or the large vessels exiting the heart. When assessing a murmur in a cat it is important to note whether it is systolic or diastolic. The origin of the murmur should also be noted; the majority of murmurs in cats are parasternal in origin, and therefore the clinician should be careful to include this area in their examination. This chapter considers causes of heart murmurs, clinical signs, assessing significance and diagnostic approach.