Prognostic values of leukocyte subset counts in peripheral blood of cancer patients have not yet been fully investigated. We retrospectively examined the relation between preoperative absolute counts of peripheral blood leukocyte subsets and clinicopathologic factors and long-term prognosis in 97 patients with liver metastasis from colorectal cancer who underwent hepatic resection. Median preoperative peripheral blood leukocyte subset counts were as follows: neutrophils 3148/mm3; lymphocytes 1574/mm3; monocytes 380/mm3. Univariate analysis indicated significantly worse 5-year cancer-related survival for patients with a peripheral blood monocyte count >300/mm3 (67.5%) than for patients with a count <or=300/mm3 (36.8%). Multivariate analysis showed a preoperative peripheral blood monocyte count >300/mm3 and preoperative CEA level (>10 ng/ml) to be independent predictive factors for cancer-related survival after hepatic resection. The preoperative peripheral monocyte count correlated positively with white blood cell and neutrophil counts, but not with the tumor number, interval between colorectal and hepatic surgery, or preoperative serum CEA level. Our findings indicate that a preoperative absolute peripheral blood monocyte count >300/mm3 is an independent predictive factor for cancer-related survival of patients with colorectal liver metastasis who have undergone hepatic resection.