Due to the capriciousness of available staining methods for the demonstration of spirochetal organisms in tissue and because of the need for a large volume staining technic, the Dieterle spirochete stain has been modified and used successfully in this laboratory for several years. This method recently gained new importance by successfully demonstrating the etiologic agent of “Legionnaires' disease” in paraffin embedded tissue after attempts made with routine stains for bacteria and fungi were not satisfactory.