M-mode echocardiography was used in 66 consecutive patients with a clinical suspicion of acute pulmonary embolism. It could be ascertained in 30 patients using pulmonary angiography and in 19 using lung scintigraphy. When pulmonary embolism had effects on haemodynamics, an end-diastolically enlarged right ventricle, a diminished left ventricle, reduced closing velocity of the anterior mitral valve cusp and paradox septum movement were seen in precordial echocardiography (n = 18). The relation of end-diastolic diameter of the right ventricle to the left ventricle correlated with the angiographic severity of pulmonary embolism (r = 0.78). In patients with acute pulmonary embolism and pulmonary hypertension a significant enlargement of the right pulmonary artery was found in the suprasternal beam direction when compared with patients without pulmonary hypertension (14.7 +/- 2.2 mm/m2 body surface vs 11.0 +/- 1.2 mm/m2 body surface; P less than 0.01). The index width of the right pulmonary artery of all patients correlated with the mean pulmonary artery pressure (r = 0.84). In one patient a thrombus in the right pulmonary artery could be demonstrated by suprasternal echocardiography. Haemodynamically effective pulmonary embolisations in patients without cardiopulmonary history can be diagnosed using echocardiography.