Serum cytokines and hepatic acute-phase responses were studied in seven patients undergoing simultaneous resection of primary gastrointestinal cancer and synchronous metastatic liver tumours and in 12 undergoing partial hepatectomy alone for metachronous hepatic metastases. The incidence of postoperative infectious complications was significantly higher after simultaneous resection than after partial hepatectomy alone (P < 0.05). Although the peak interleukin 6 level was significantly higher after simultaneous resection (P < 0.05), plasma levels of acute-phase proteins were significantly lower (P < 0.05). The results suggest that simultaneous resections further reduce the hepatic acute-phase response and render patients liable to infection compared with partial hepatectomy alone, and result in a higher incidence of postoperative infective complications.