['This study was to assess the clinical relevance of the blood granulocytes to lymphocytes (G/L) ratio as an early marker of surgical stress in patients with colorectal cancer.', 'Thirty-three patients with colorectal cancer were prospectively to undergo laparoscopic-assisted (n=12) or open (n=21) surgical resection. Granulocyte and lymphocyte counts were used to calculate the G/L ratios in blood samples from all patients before the operation and post-operatively on days 1, 3 and 7. Additionally, serum inflammatory cytokines, interleukin (IL)-1β, IL-6, IL-8, tumour necrosis factor (TNF)-α, granulocyte colony-stimulating factor (G-CSF) and macrophage (M)-CSF were assayed as markers of surgical stress.', 'Seven of 33 patients developed unexpected complications. Serum IL-6 (P<0.0001), G-CSF (P=0.0257), and M-CSF (P<0.0001) were higher on day 1 vs before the operation. Similarly, the G/L ratios were higher on days 1-3 vs before the operation (P<0.0001) and then gradually decreased together with the surgical stress levels. The G/L ratios and the numbers of granulocytes and lymphocytes in the blood showed no correlation with serum IL-1β or TNF-α. In contrast, the G/L ratios and the numbers of granulocytes in the blood showed significant correlation with IL-6 (Rs=0.710, P<0.0001, Rs=0.653, P<0.0001, respectively), with G-CSF (Rs=0.626, P<0.0001, Rs=0.578, P<0.0001), with M-CSF (Rs=0.470, P<0.0001, Rs=0.372, P<0.0001). However, the number of lymphocytes showed inverse correlation with IL-6 (Rs=-0.493, P<0.0001), G-CSF (Rs=-0.440, P<0.0001) and M-SCF (Rs=-0.443, P<0.0001).'] Is the perioperative granulocyte/lymphocyte ratio a clinically relevant marker of surgical stress in patients with colorectal cancer?