In this review, we demonstrate that there is no universal diagnostic strategy for non-severe acute pulmonary embolism. The first part of the article is devoted to the concept of thromboembolic disease: its frequency, severity and diagnostic difficulties. The second part analyzes the tools used for diagnosis of pulmonary angiography, noninvasive venous studies, and helical CT angiography. The last part discusses current diagnostic algorithms for pulmonary embolism and the changes that may be introduced by the use of helical CT in clinical practice. The potential for MR imaging id discussed.