Human lung tissue containing the Legionnaires disease bacterium was fixed in seven different histological fixatives, processed, and embedded in paraffin. Deparaffined sections from each were stained by fluorescent antibody and by Dieterle silver impregnation. With the fluorescent antibody stain, the Legionnaires disease bacterium could be detected in tissues prepared with any of the fixatures, but the Dieterle silver impregnation was not satisfactory on Zenker-fixed tissues.