Primary pulmonary hypertension (PPH) is essentially a diagnosis of exclusion and usually is made late because of the nonspecific nature of the early signs and symptoms. Echocardiography is a key screening test in the diagnostic algorithm of patients with suspected PPH. The purpose of this study was to define the echocardiographic Doppler features in patients with PPH at the time of diagnosis. From 1992 to 1997, 51 patients were diagnosed with PPH at our institution. All underwent a standardized transthoracic echocardiographic examination, including a contrast study and transthoracic echocardiographic examination if indicated. Pulmonary artery systolic pressure was calculated from the tricuspid regurgitation jet. The majority of patients had pulmonary artery systolic pressure greater than 60 mm Hg (96%) associated with systolic flattening of the interventricular septum (90%), enlarged right atrium (92%) and ventricle (98%), and reduced right ventricular systolic function (76%). There was an increase in the interventricular septal thickness (>1.2 cm) in 21 (43%) of 49 patients, accompanied by a septal/posterior wall ratio greater than 1.3 in 11 (22%) of 49. Although a reduction in both left ventricular systolic and diastolic volumes was noted, global left ventricular systolic function was preserved in all patients. Mitral E/A ratio was less than 0.7 in 7 (22%) patients studied. Color Doppler revealed moderate to severe tricuspid regurgitation and pulmonic insufficiency in 41 (80%) of 51 and 16 (31%) of 51 of cases, respectively. Pericardial effusion (7 small and 1 moderate) and patent foramen ovale (n = 12) were also frequently detected. At the time of initial diagnosis, PPH is associated with secondary cardiac abnormalities in the majority of patients.