The diagnosis of pulmonary embolism (PE) is still an unresolved problem. The aim of this prospective observational study was to derive and validate a prediction rule (PEscore) by which PE can be diagnosed by easily obtainable and rapidly available investigations. Included were consecutive patients with a clinical suspicion of PE admitted to a community hospital. Risk factors and clinical and instrumental investigations were registered. PE was diagnosed by angiography, scintigraphy, or autopsy. In 168 patients, PE was either diagnosed (angiography, n = 28; autopsy, n = 18) or excluded (angiography, n = 12; scintigraphy, n = 99; autopsy, n = 11). Based on the results of clinical and instrumental findings, a PEscore was derived by a multiple regression analysis, calculated as: [0.29 x proven leg vein thrombosis (0 = no, 1 = yes)] + [0.25 x ECG right heart strain (0 = no, 1 = yes)] + [0.22 x neck vein distension (0 = no, 1 = yes)] + [0.20 x dyspnoea (0 = no, 1 = yes)] + [0.13 x suspicious chest X-ray (0 = no, 1 = yes)] - [0.17 (constant)]. The PEscore was tested further in 139 subsequent cases. In these patients, the PEscore was 0.65+/-0.17 (diagnosed PE, n = 47) and 0.18+/-0.17 (excluded PE, n = 92), respectively (p = 0.0001). Depending on a given PE-score, the level of probability of PE can be assessed. Calculation of the PEscore can be helpful in clinical decisions when PE is suspected.