Although intrahepatic infusion therapy with 5-fluorouracil for unresectable colorectal liver metastases may lead to improved overall survival for some patients, it is not clear why a response is not observed in others. Gene alterations in oncogenes or tumor-suppressor genes are critical events in tumor formation, and some of them could play a role in the process of drug resistance. The tumor-suppressor gene p53, which is known to trigger cell arrest or apoptosis in response to DNA damage, is found to be mutated in a wide range of human tumors. The aim of this work is to establish whether a relationship is found between p53 mutations and survival in patients undergoing adjuvant chemotherapy for advanced Dukes' D colorectal cancers. Seventeen tumors from patients treated with 5-fluorouracil regimen via intrahepatic infusion for unresectable colorectal hepatic metastasis were considered. p53 mutations from tumor DNA were detected, after amplification by PCR of exons 5 to 8, by non-radioactive single-strand conformation polymorphism and direct DNA sequencing. Patients with mutated p53 colorectal tumors had short survival, whereas prolonged survival was associated with the presence of wild-type p53 (p = 0.019). Our data suggest that mutated p53 colorectal tumors had a weak response, or even no response, to chemotherapeutic treatment. Routine assessment of p53 status would be helpful in selecting patients with only wild-type p53 gene who have a predictably better response to chemotherapy.