Inactivation of SV40 large T antigen, in cells immortalized with conditional mutants, leads to activation of p53 and apoptosis. We have analyzed during this process the expression of genes induced by p53 or differentially expressed during apoptosis in other systems. We find an early induction of Waf1/Cip1. We also observed clusterin is induced late during the process and displays a high level of expression in non-apoptotic cells suggesting a protective role for clusterin. Other genes identified during thymocyte and lymphocyte apoptosis are not induced, showing that the pattern of gene induction is specific to the system studied.