The aim of this study was to investigate the effect of the cyclo-oxygenase inhibitor ibuprofen on the acute-phase protein response and resting energy expenditure (REE) of weight-losing patients with pancreatic cancer. Patients with irresectable pancreatic cancer (n = 16) were treated with either ibuprofen (1200 mg day-1 for 7 days (n = 10) or placebo (n = 6). A group of 17 age-related non-cancer subjects were also studied. Indirect calorimetry, anthropometry, multifrequency bioelectrical impedence analysis and serum C-reactive protein (CRP) estimation were performed immediately before and after treatment. Before treatment, total REE was significantly elevated in the pancreatic cancer patients compared with healthy controls (1499 +/- 71 vs 1377 +/- 58 kcal) (P < 0.02). Following treatment the mean REE of the ibuprofen group fell significantly (1386 +/- 89 kcal) compared with pretreatment values (1468 +/- 99 kcal) (P < 0.02), whereas no change was observed in the placebo group. Serum CRP concentration was also reduced in the ibuprofen-treated group (pre-ibuprofen, 51 mg l-1; post-ibuprofen, 29 mg l-1; P < 0.05). These results suggest that ibuprofen may have a role in abrogating the catabolic processes which contribute to weight loss in patients with pancreatic cancer.