A new cell line, designated as Tuwei00, is described. It originated from an Epstein-Barr virus-positive skin tumor biopsy of a heart transplant recipient, whose numerous cutaneous neoplasms were treated with the antiviral drug cidofovir what caused at least transient remissions. The cell line was established in vitro and maintained for more than 70 passages. Cells of early passages were characterized by a slower growth, the inability to form colonies and a higher sensitivity to cidofovir. After overcoming a crisis, the cells grew faster, to a higher density and were able to form adherent colonies from single cells as well as colonies in soft agar. Chromosome analysis showed diploidy/hyperdiploidy at the earlier and hypodiploidy at the later passages. Sensitivity to cidofovir was distinctly higher in early passages of Tuwei00 cells than in later passages and was characterized by distinct decline of cell survival after long term cidofovir exposure. Established normal human keratinocytes, HaCaT cells, which were checked for comparison, showed a low cidofovir sensitivity similar to late passage Tuwei00 cells.