Inactivation of SV40 large T antigen in cells immortalized with conditional mutants leads to activation of p53 and apoptosis. We have analysed 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 observe clusterin is induced during the process and displays a high level of expression in non-apoptotic cells, suggesting a protective role for clusterin. Other genes associated with thymocyte and lymphocyte apoptosis are not induced, showing that the pattern of gene induction is specific to the system studied.