The Authors have used, on a group of 51 patients, a score-system for the clinical diagnosis of pulmonary embolism. This system is based on clinical examination of the patients and utilizes a different value for each sign and symptom: each sign and symptom correspond to a positive number. Every patients was also undergone instrumental tests to confirm the diagnosis (i.e.: perfusion lung scanning and venous doppler) according to previously defined diagnostic program. A good relationship between the instrumental diagnosis and clinical probability was found with above mentioned score-system. The AA believe that this score-system is valid and that it can be used in elaborating diagnostic decision, particularly in those cases in which the diagnosis is not established by the instrumental tests and in which is not possible to perform pulmonary angiography.