BACKGROUND: There has been reports which suggest that non-specific symptom of patients with mitral valve prolapse is associated with autonomic dysfunction. METHODS: To assess autonomic dysfunction of patients, we examined five cardiovascular reflex tests in 25 asymptomatic MVP patients(identified as MVP group), 25 symptomatic MVP patients(identified as MVP syndrome group) and 25 control group. RESULTS: In the five cardiovascular autonomic function tests, abnormalities of Valsalva ratio were detected in 1(4%) control group, 7(28%) MVP group, 9(36%) MVP syndrome group, heart rate response to deep breathing in 0(0%), 2(8%), 4(16%) respectively, immediate heart rate response to standing in 0(0%), 2(7.4%), 2(8%) respectively and in postural hypotension, there were no abnormal group. Abnormalities of blood pressure response to sustained handgrip were only detected in 2(8%) MVP syndrom group. According to the five categories of cardiovascular autonomic functon tests, normal in 24(96%) and early damage in 1(4%) were detected in control group. In the MVP group, normal 17(68%), early damage 6(24%) and definite damage 2(8%) were noted. In the MVP syndrome group, normal 9(36%), early damage 13(52%), definite damage 1(4%) and combined damage 2(8%) were detected. In case of heart rate response to deep breathing, we found significant differences between control and MVP syndrome group(p=0.043), and between MVP and MVP syndrome group(p=0.0043). In case of heart rate response to standing, between control and MVP syndrome group(p=0.0009), between MVP and MVP syndrome group(p=0.001), the differences were noted. In case of blood pressure response to standing, between control group and MVP group(p=0.0019), between MVP and MVP syndrome group(p=0.0075), we found significant differences. Resulting from our study, heart rate response to deep breathing and standing, blood pressure response to standing were of considerable value in assessing the autonomic dysfunction of patients with mitral valve proapse. CONCLUSION: We found autonomic dysfunction in addition to increased autonomic tone and responsiveness which have been already known previously in mitral valve prolapse. And autonomic dysfunction was more severe in symptomatic patients with mitral valve prolapse than asymptomatic ones.