[en] The authors describe the use of proton-induced X-ray emission (PIXE) to analyse the nickel concentrations of the autopsy specimens from victims of Legionnaires' disease. They show that the high nickel concentrations in the lung specimens from the first recognized Legionnaires' cases in Philadelphia in 1976 were due to contamination during the autopsies. Recently the authors have used PIXE to show that the selenium concentrations in the sera of the acutely ill Legionnaires' patients are significantly lower than in their matching convalescent-phase sera. This finding may be related to the patient's response to the disease or to the specific characteristics of the Legionella pneumophila itself. Studies show that the disease is not a rare illness but a worldwide one. General criteria concerning specimen collection are described