Abstract
The susceptibility of freshly isolated human epithelial cells to simian virus 40 (SV40) transformation is very low (1–5). It has been difficult to quantitate the sensitivity of these cells to SV40 transformation, since the end point is indefinite life span in vitro. None the less, the phenomenon is considered to be a relatively rare event, which may occur in 1 to 10% of cultures inoculated, and with substantially lower frequency within any single culture population.