The close association between HPV-16 and cervical cancer implies some role for the virus in development of this cancer. Recent studies have shown that the HPV-16 E7 gene encodes the major transforming activity of the virus in baby rat kidney (BRK) cell transformation assays. To investigate the requirement for continued E7 expression in BRK cells transformed by HPV-16 E7 plus EJ-ras, we have developed a system for inducible expression of the E7 gene. The studies reported here show that continued expression of the HPV-16 E7 gene is required for maintenance of the transformed phenotype in these cells. The implications these observations bear on the role of the E7 gene in cervical carcinoma are discussed.