We conducted a study to evaluate a noninvasive strategy including spiral computed tomography (CT) in patients with suspected pulmonary embolism (PE). We systematically performed spiral CT, ventilation/perfusion lung scanning, and D-dimer (DD) measurement (VIDAS test), and in some cases (with a normal CT with nondiagnostic lung scan and increased DD) performed venous ultrasonography (US) on 247 consecutive patients with clinically suspected PE in our hospital. Patients in whom PE was deemed absent were not given anticoagulants. All patients were followed for 3 mo. The prevalence of PE in the 228 patients who could be evaluated was 42% (96 of 228). PE was confirmed by spiral CT in 73% of the patients, by a high-probability lung scan in 4%, and by findings on US in 23%. PE was ruled out by a normal lung scan in 14% of the patients, by a normal DD concentration (< 500 ng/ml) in 31%, by an obvious differential diagnosis on spiral CT in 18%, by a similar prior lung scan in 11%, and by the combination of normal spiral CT findings, a nondiagnostic lung scan, a DD concentration > 500 ng/ml, and normal US in 26%. Pulmonary angiography was performed in only two patients, both of whom had a normal spiral CT scan and a high-probability lung scan, and was normal. The 3-mo risk of thromboembolism in patients not given anticoagulants, based on the results of the diagnostic protocol, was 1.7% (95% confidence interval: 1.5 to 2.3%). There were no deaths. The noninvasive strategy of combining spiral CT, lung scanning, DD measurement, and in some cases US, in patients with suspected PE yielded a definite diagnosis in 99% of patients, and appeared to be safe.