The value and role of clinical findings in the diagnosis of pulmonary embolism were analysed in the three steps of clinical reasoning: firstly, they lead the physician to suspect the diagnosis; however, no sign or association of clinical signs allow confirmation or infirmation of the diagnosis; they are simply a guide to diagnosis; secondly, they contribute to the exclusion of a number of differential diagnoses, with the help of simple complementary investigations such as blood gases, electrocardiograms and chest X-ray; finally, when grouped together and expressed in terms of probability, clinical data are essential for the interpretation of pulmonary scintigraphy and for assessing the indications of further investigations.