Prognostic factors of unresected liver metastases in patients with colorectal cancer are not well established. A total of 544 patients with unresected liver metastases from colorectal cancer were registered in a national survey over a 1-year period and followed until death. Twenty factors were studied in a univariate analysis (log rank test) and 16 influenced survival (P < 0.01). These 16 factors were entered in a multivariate analysis (Cox model) and eight, ranging from the most significant (relative risk of death 1.9) to the less significant (relative risk of death 1.2), independently influenced survival: performance status, alkaline phosphatase level, number of involved liver segments, administration of chemotherapy, presence of extrahepatic metastases, site of the primary tumour, prothrombin time and resection of the primary lesion. Two simple classifications are proposed, taking into account the performance status and the alkaline phosphatase level, or the performance status and the number of involved liver segments.