A wide variety of arrhythmias as well as exercise induced hypotension were described in some Mitral Valve Prolapse (MVP) patients. The aim of our study was to evaluate the correlation between the incidence of arrhythmias and the decrease of Systolic Blood Pressure (SBP), ST-T changes and prolonged QTc interval. 50 MVP patients (diagnosis confirmed by M-mode and 2-D echocardiography) underwent a complete clinical evaluation, 12 lead standard ECG, 24 hr. monitoring ECG and a submaximal exercise test. On the basis of the SBP response to effort, the patients were divided into 2 groups (gr.): gr. A, 18 patients with a decrease of the SBP during effort, mean 135 +/- 16.5 mmHg and gr. B, 32 patients with a normal increase of the SBP at the end of the effort, mean 168 +/- 14.7 mmHg (p less than 0.001). Arrhythmias were found in 83.33% among patients in gr. A and in 50% in gr. B (p less than 0.05). We did not find a significant difference concerning the types of arrhythmias between the 2 groups. Exercise induced ST-T changes, appeared in 55.55% in gr. A and in 25% in gr. B (p less than 0.05) but the incidence of arrhythmias in patients with ST-T changes was not significantly different between the 2 groups (5.55% and 6.25% respectively). Rhythm disturbances were found in 3 out of 4 patients with prolonged QTc in gr. A and in 2 out of 4 patients in gr. B (p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)