The postmortem diagnosis of fat embolism syndrome (FES), traditionally based on the histological demonstration of fat globules, needs a quantitative analysis of both the size and localization of the fat emboli, which is essential for a reliable grading of the pulmonary fat embolism. The clinical data and the autopsy records of 2738 autopsies were retrospectively evaluated, and 21 cases in which FES was pointed out as cause of death were selected and compared with 21 fatal cases referred to as major trauma in which the cause of death was not attributed to fat embolism, and with 47 fatal cases as control group, respectively. The following parameters were investigated: the total area of the embolized tissue; the total number of emboli; the mean area of the emboli; the mean percentage of the embolized tissue area as compared with the total tissue area of each sample; the total percentage of the embolized tissue area as compared with the total tissue area of all slides. The most reliable parameters seem to be the ratio between embolized tissue areas as compared with the total tissue area of each sample. These parameters showed a good correlation with the clinical data.