The p53 tumor suppressor gene is frequently mutated in most human malignancies. These mutations have been associated with clinical outcome for various cancer types. Since this gene's main function is to guard the integrity of the genome, its clinical relevance, i.e. its role in carcinogenesis and chemotherapy-drug resistance, have been extensively studied. These data and the p53 protein as a potential target for new treatment strategies, are reviewed based on acquired knowledge of the structure function of the p53 protein.