Pulmonary profusion scintigraphy is a simple, noninvasive and low-cost method for identifying acute pulmonary embolism. Although the method is highly sensitive, it is relatively non-specific, so that final assessment must include history, clinical findings and plain roentgenography of the thorax. Pulmonary scintigraphy is indicated whenever acute pulmonary embolism is suspected, on account of the therapeutic consequences resulting therefrom, in all cases where clinical findings and basic diagnosis cannot definitely establish the disease. It must not, however, be considered as an alternative to angiography of the pulmonary artery; as a matter of fact, it should be employed early and frequently in view of the high percentage of undiagnosed embolism of the lungs during the patients' lifetime.