Seldom mentioned as a possible etiology of false positive stress tests (ST), the right atrial hypertrophy (RAH) may cause electrocardiographic aspects evocative of myocardial ischemia in the lower areas. The retrospective study concerns STs in 4 patients, staying in a cardiac rehabilitation center, following (D14) surgery for isolated type II IAC, Fallot's trilogy (n = 1), or dual valvular disease (tricuspid insufficiency and mitral stenosis, n = 1), and presenting all on basal ECG a RAH (group I). These STs are compared to that of a reference group operated (D14) from a IAC type II (isolated n = 3, associated to RVPA n = 1), but without signs of RAH on the rest ECG (group II). All other possible causes of electrically positive STs were eliminated from this study. In patients with RAH, the stress test is positive in the lower area (ST = -1.27 +/- 0.25 mm). In four other patients without HAD, the STest is negative in 3 cases and uncertain in one. These results do not seem to be linked to pre-operative hemodynamic data, nor to sonocardiographic data. Atrial repolarization alone seems to be the cause of these ECG alterations during stress, as demonstrated, in one patient, by sudden variations of the ST segment during a change from an atrial rhythm (AR) (with retrograde atrial depolarization) to a sinus rhythm (SR). These observations suggest the role of atrial repolarization in the origin of false positive stress tests in patients with RAH.