Background: The optimal duration, safety, and benefit of preoperative chemotherapy in patients with colorectal liver metastases (CLM) are unclear. We evaluated the association between the duration of preoperative chemotherapy with 5-fluorouracil (5-FU), leucovorin, oxaliplatin (FOLFOX) ± bevacizumab, pathologic response, and hepatotoxicity after hepatic resection for CLM. Methods: A total of 219 patients underwent hepatic resection following FOLFOX with or without bevacizumab and were divided into 2 groups according to the chemotherapy duration: 1-8 cycles (short duration [SD]; N = 157) and ≥ 9 cycles (long duration [LD]; N = 62). The frequency of complete or major pathologic response, sinusoidal injury, and major postoperative morbidity were compared. Results: Treatment consisting of ≥9 cycles was not associated with an increase in complete or major pathologic response (SD vs. LD, 57% vs. 55%; P = .74). The incidence of sinusoidal injury was higher in the LD group (26% vs. 42%; P = .017). The incidence of liver insufficiency was higher in the LD group (4% vs. 11%; P = .035). Sinusoidal injury did not predict postoperative liver insufficiency; multivariate analysis revealed ≥ 9 cycles was the only independent predictor of postoperative liver insufficiency (P = .031; odds ratio = 3.90). Chemotherapy including bevacizumab was associated with a significantly higher frequency of complete or major response in both SD and LD groups. Conclusions: Extended preoperative chemotherapy increases the risk of hepatotoxicity in CLM without improving the pathologic response. The type of chemotherapy (FOLFOX with bevacizumab) has more impact on pathologic response than the duration of chemotherapy. © 2010 Society of Surgical Oncology.