Different patterns of left-ventricular (LV) diastolic dysfunction were reported in patients with pulmonary hypertension (PHT). There are no data regarding the relationship between the severity of PHT and LV diastolic dysfunction. In order to determine the severity of PHT at which LV diastolic dysfunction occurs and to identify its pattern, we studied by Doppler echocardiography 120 patients with PHT (57 with severe PHT and 63 with mild or moderate PHT) and compared them with 75 normal controls. Systolic pulmonary artery pressure (SPAP) was measured by tricuspid regurgitant jet method and the usual transmitral LV diastolic indices were recorded. LV diastolic dysfunction of impaired relaxation type is most commonly seen in patients with severe PHT. No differences were observed between patients with mild and moderate PHT regarding LV diastolic function. A SPAP ≧60 mm Hg is needed to induce changes in the LV diastolic filling pattern.