Poor R wave progression in the right precordial leads has frequently been reported in patients with pure mitral stenosis, but has never been investigated from clinical and hemodynamic points of view. In this work the clinical, electrocardiographic and hemodynamic data of 19 patients (mean age: 49 +/- 8.6 years), with pure mitral stenosis and poor R wave progression (study group) were compared with those of 19 subjects with pure mitral stenosis and normal R wave progression (control group). The age, sex distribution and duration of mitral valve disease were similar in the two groups; also clinical status, i.e. the distribution in the functional classes (NYHA), was similar in the two groups. Mitral valve area was similar in the two groups (1.3 +/- 0.5 vs 1.1 +/- 0.3 cm2), whereas wedge pressure, mean pulmonary artery pressure, systolic and diastolic right ventricle pressures and total pulmonary resistances showed significant lower values in patients with poor R wave progression compared to those with normal R wave progression (P less than 0.05). The hemodynamic variables of left ventricle and the cardiac index were similar in the two groups. In study group patients there was higher prevalence of vertical axis (P less than 0.05). These data indicate that in pure mitral stenosis, clinical status is similar in patients with poor R wave progression and in those with normal R wave progression, whereas in the former there is slighter hemodynamic involvement of the right ventricle.