A 43-year-old man was admitted because of severe and recurring haemoptysis, which was eventually ascribed to Goodpasture's syndrome. In case of an aspecific sign such as haemoptysis experienced clinicians will try to restrict the differential diagnosis by concentrating on other signs that are relevant to the main problem. In haemoptysis these other signs are general illness, fever, shortness of breath, painful respiration, chronic productive cough, and signs or a history of cardiac or pulmonary disease. If the differential diagnosis consists mainly of rare disorders or rare manifestations of common disorders, all possibilities should be considered. If Goodpasture's syndrome is suspected, further specific diagnostic tests should be done without delay.