The history of experimental fat embolism dates as far back as 1669, when Lower1 did some work on lipemia and its effect on the circulation in animals. Since that time a tremendous amount of work has been done,2 both clinically and experimentally, on the accurate detection of fat embolism. As far as we know, roentgen examination has never been used for this purpose. Therefore we are presenting for the first time the results of experimental work which show the value of the roentgenograms of the chest in the diagnosis of fat embolism. EXPERIMENTAL PROCEDURE AND RESULTS We used eleven dogs in our experiments, selecting whenever possible an animal weighing close to 12.5 Kg. Sterile oleic acid was given intravenously to six animals and sterile olive oil to five. Doses of varying amounts were used in each experiment. Owing to the researches of Landois,3 who found that olein