The intraosseous ganglion is a cystic lesion of bone most frequently located in the subchondral epiphysis of long bones without direct communication with a joint cavity. Although this entity is becoming well recognized by orthopedic surgeons and radiologists, it has rarely been discussed in the pathologic literature and is frequently overlooked by the surgical pathologist. In this study the clinical and pathologic features of 10 patients, representing 11 instances of intraosseous ganglia, were reviewed with emphasis on the histologic and radiologic features necessary for diagnosis. Common radiologic features usually include a unilocular cyst surrounded by a thin rim of sclerotic bone in the subchondral epiphysis in the absence of other features of degenerative joint disease. Histologically, the ganglia are usually composed of a cystic space without epithelial lining, often filled with gelatinous, mucoid material and occasional foamy macrophages. The radiologic and histologic differential diagnoses, possible etiologic factors, and treatment are discussed.