To clarify the histopathological, clinical behavior biological characterics and the relationship among the psammomatoid ossifying fibroma (POF), ossifying fibroma and fibrous dysplasia of bone.Thirty-one cases of POF in the ear and sinonasal region were studied retrospectively. The sections, clinicopathological records from June, 1956 to November, 1996 were reviewed. The reticulum fiber and Masson's stain and alkaline phosphatase immunostain were done in 10 cases, Vimentin, Desmin, EMA and smooth actin immunohistochemical stain were done in 5 cases. One case was studied by transmission electron microscope.The specimens were broken tissue with the sand-like felling, eleven specimens with intact thin shell consisted of bone tissue were used to study the changes in the area between tumor and normal bone. Histopathologically they were rich in mesenchymal tumor cells and a lot of calcifying psammomatoid-like osteoid and a few of calcified bodies similar to those described by Shafer, and the bony trabecula was not found in the center of the tumor. In addition, three zones were noted at the junction of normal bone and tumor, namely, the normal bone-reactive proliferative bone-tumor. In some cases, the reactive bony proliferation may be not marked. The normal bone adjacent to the tumor may be absorbed and disappeared, and were then replaced by the tumor, and finally led to tumor tissue invasion into the soft tissue, but the infiltration appearance is not present.POF is the slowly growing benign tumor and is different from ossifying fibroma and fibrous dysplasia of bone.