[en] Over a one-year period, 206 patients with suspected pulmonary embolism received gamma camera perfusion lung images on an emergency 24 hr. basis. Clinical diagnosis listed pulmonary embolism in 37 of 39 patients whose images showed a high probability of it, in 28 of 69 whose images were abnormal but rated uncertain probability, and 5 of 98 with normal images. Retrospective clinical evaluation indicated 89 of the emergency images to be considered important, 95 contributory, and 22 not helpful in clinical management. As a result of the images, 80 patients were placed on heparin therapy of 198 considered for it, and 22 of 29 patients referred for hospital admission were placed on an outpatient basis. Delay in obtaining lung images creates the possibility of diagnostic uncertainty in interpreting the image