In this prospective echocardiographic study, we investigated the occurrence of mitral valve prolapse (MVP) in 60 dachshunds: 30 with mitral regurgitation (MR), 15 age-matched and 15 3-year-old controls without heart murmurs. To assess the MVP, video recorded sequences from the right parasternal long axis 4-chamber view were blindly evaluated by three observers. Of the 30 dogs with MR, 12 (40%) had severe MVP, 10 (33%) had mild MVP, and eight (27%) had a normal mitral valve. The clinical status of the dogs with MR correlated significantly with the severity of MVP, and these dogs had significantly worse MVP than age-matched controls, among which seven (47%) had mild MVP and eight (53%) had a normal mitral valve ( P < 0.01). In the group of 15 young dachshunds without heart murmurs, seven (47%) had mild MVP and eight (53%) had a normal mitral valve. The degree of MVP correlated significantly with the occurrence of arrhythmias, particularly severe sinus arrhythmia. We conclude that dachshunds with MR have a higher prevalence of MVP than controls, and that the severity of MVP is correlated with clinical status. The dogs with MVP and marked sinus arrhythmia might have autonomic dysfunction, analogous to findings in humans. Whether young dachshunds with MVP are predisposed to MR later in life must await the results of a longitudinal study.