Starting from 1969, the yearly number of patients with pulmonary embolism documented in the S. Chiara Hospital of Pisa is increased, in spite of the unchanged diagnostic procedures. Aim of this work is to verify if this trend is accompanied by earlier diagnosis with an improvement in the clinical outcome of pulmonary embolism, and if a relevant diagnostic failure is still present in our hospital. A comparison of pulmonary embolism cases collected from 1969 to 1971 and from 1980 to 1982 showed that the number of diagnoses made within one week from the onset of symptoms is increased (+24.8%), whereas the number of diagnoses made after more than one month is reduced (-18.1%). At the same time we observed that cases with a standard PaO2 less than 40 mmHg are reduced (-23.1%) while cases with a standard PaO2 greater than 50 mmHg are increased (+29.9%). An earlier diagnosis of pulmonary embolism contributed to treat a larger percentage of patients (+29.7%) and to lower the early mortality (-17.4%). This diagnostic trend can be ascribed to an increased readiness in raising the clinical suspicion of pulmonary embolism and to the prompt availability of perfusion lung scan, that is the center of our diagnostic strategy. Data of our 1,010 patients, compared with those of autoptic series and with the number of admissions, surgical operations and deaths in the wards of our hospital, suggest some persistent diagnostic failure in patients with well documented embolic risk; such as injured, burned, patients affected by neoplasm or motor lesion, patients operated for orthopedic or gynaecologic problems.