In the present study the establishment and characterization of a new oxyphilic papillary thyroid carcinoma cell line--ONCO-DG1- is given. With immunohistological, histochemical and flow cytometric methods, ONCO-DG 1 cells revealed features of epithelial differentiation. Furthermore the cells formed von Kossa-positive deposits resembling psammoma bodies in monolayer and spheroid culture until late passages. The tumor cell line is now in the 40th subculture. Because of the ability to form multicellular tumor spheroids (MCTS), this cell line is a good model for examining the interaction between thyroid tumor cells and confluent human endothelial cells on extracellular matrix in vitro. It is also suitable for xenotransplantation studies, because it is tumorigenic in NMRI nude mice in vivo.