The influence of transfusion of lymphokine-activated T killer cells (T-LAK) on inflammatory responses was examined in dogs after laparotomy. Plasma C-reactive protein (CRP) level, cell numbers of peripheral blood lymphocytes (PBLs) and T lymphocyte subsets (CD3(+), CD4(+) and CD8(+)) and mRNA expression levels of cytokines including interleukin (IL)-2, IL-12, IL-4, IL-10 and transforming growth factor (TGF)-β in peripheral blood mononuclear cells (PBMCs) were measured in dogs with (T-LAK group) or without (control group) a single T-LAK administration immediately after laparotomy. The plasma CRP level initially increased and then decreased to the normal range at 7 days after laparotomy in the T-LAK group, which was earlier than in the control group. The expression level of IL-10 mRNA showed a marked postoperative increase and was significantly higher than the preoperative level on day 7 (P<0.05), whereas the level in the control group showed no clear change after laparotomy. A significant increase in IL-2 mRNA expression level in the T-LAK group was observed on day 14, which was two weeks earlier than in the control group (P<0.05). These results suggest that T-LAK therapy in dogs after laparotomy leads to earlier resolution of postoperative inflammation by production of an anti-inflammatory cytokine (IL-10) in the early phase of the postoperative period and earlier restoration of cell-mediated immunity related to cytokine production by PBMCs.