An immunofluorescent staining method for detecting platelet-activating factor (PAF) is described. This method employs a polyclonal anti-PAF rabbit antibody. When rat brain, heart, lung, liver or kidney tissue was stained using this method, the heart, lung and kidney exhibited PAF-specific staining. Analysis of the amount of PAF in different organs, either by immunofluorescence or by bioassay, showed that kidney tissue contains the greatest amount of PAF.