A new index of tumorigenic potency is derived using a survival-adjusted quantal response estimator given by Bailer and Portier (1988, Biometrics 44, 417-431). The small-sample bias and mean squared error properties of this estimator are explored using computer simulations of animal carcinogenicity experiments and are compared to the characteristics of the TD50, an estimator proposed by Sawyer et al. (1984, Biometrics 40, 27-40). It is observed that this new index tends to have smaller bias and mean squared error relative to the TD50 over varying shapes of the tumor onset distribution, levels of tumor lethality, and levels of treatment lethality.