Discusses a study which suggests that small-molecule drugs can be designed to activate p53 protein by preventing the binding of a negative p53 regulators called Mdm2. Prospects of new non-genotoxic general treatments of cancer; Mechanism of p53 protein as a tumor suppressor; Identification of a family of synthetic compounds which called Nutlins; Subtle effect of a hypomorphic allele of the Mdm2 gene on the p53 response.