A new cultured cell line (HuOS) was established from tumor cells obtained from the pulmonary metastatic foci of a patient diagnosed as chondroblastic osteosarcoma. The tumor cell line was maintained for over 19 months, and morphological and biological characteristics were studied. These cells retained their malignant properties and produced nodules when transferred intramuscularly to nude mice. Morphologically, these nodules revealed a chondromatous pattern.