Cells from a salivary gland pleomorphic adenoma with a reciprocal translocation, t(8;12)(q22;q14), were transformed by transfection with a plasmid containing the SV40 "early region." Compared with nontransformed adenoma cells, the cells expressed large-T antigen, had a higher proliferative capacity, showed a drastically increased or even unlimited growth potential in vitro, and formed colonies in soft agar. The amount of cellular material produced in this way should make possible many experiments at the molecular level that could not be performed before.