In this study, the prevalence of the mitral valve prolapse (MVP) was investigated in dogs. A total of 284 dogs with various cardiac signs (no complaint or cough, respiratory distress, fever, fainting and limitation of movement) were examined from March 1998 to August 2009 by echocardiography. The MVP prevalence was 70.8% (201 cases): the classical form (leaflet prolapse into the left atrium between 0.5 and 0.8 mm) was observed in 151 dogs and a severe form (leaflet prolapse above 1.0 mm) was found in 50 dogs. Furthermore, 116 dogs with MVP also exhibited a mitral insufficiency. On the other hand, a weak mitral valve prolapse (below 0.5 mm) was also evidenced in 41% (34 cases) of dogs considered as not MVP affected (83 dogs). The MVP incidence was more elevated in animals older than 10 years, in males than in females and in some specific breeds for the classic form, especially in the West Highland White terriers. These results demonstrate the high incidence of the MVP in dogs and the occurrence of a minor form in dogs without clinical signs. emphasizing in this way the pertinence of echocardiography examination in dogs.