The aim of the study was to assess the hypothetic relationship between right atrial mechanoreceptors stimulation due to mild to moderate tricuspid regurgitation and forearm venous tone. Method: The study group included 15 patients (9 males, 6 females, average years range 25-55) with mild to moderate tricuspid regurgitation (TR) measured by EchocardioDoppler examination (CW maximum regurgitation velocity included between 2.0 and 3.6 m/s). The study group was compared with sex and age matched control group (N) with no or trivial tricuspid regurgitation (CW maximum regurgitation velocity <2.0 2.0 m/s). Exclusion criteria were: congenital heart disease, heart failure, pericardial disease, cardiac arrhythmias, arterial peripheral, Venous disease, neuro-vascular compression syndrome. In condition of no pharmacological treatment each patient was submitted to mercury straingauge plethysmography (PSG) at 20-40-60 mmHg venous occlusion straingauge; straingauge was applied at maximum right forearm diameter at zero phlebostatic level right atrium). Each examination was performed after 10’ of rest (forearm abduction <30°; physiological breath; temperature: 24-26 °C). We calculated the following plethysmographic parameters: venous distensibility (VD) and venous tone (VT) at 60-40 mmHg occlusions, time of total emptying (tTE) at 60 mmHg occlusion and venous pressure (VP) estimated by a linear regression on 20-40-60 MVIV (maximal venous incremental volume) points. The exams were performed by 2 operators in single blind. The T test for unpaired data was performed for statical analysis. Results: our data showed in TR group a significant increase of VD (25.5%. p<0.05) and of tTE (91.8%, p < 0.05), decrease of VT (29.6%, p < 0.05), without difference in VP. Conclusion: this phenomenon can be explained as consequence of a loss in venous-constrictor sympathetic drive on venous wall probably related to stimulation or right atrial mechano-receptors.