Colonoscopy is often disturbed by poor patient tolerance; benzodiazepines or opiates are routinely used to overcome such problems, despite the possibility of undesired effects. Tramadol, an opiate analogue with potentially fewer side effects, has not been tested yet to this end. The aim of the study was therefore to evaluate the efficacy of tramadol as a premedication for the colonoscopic procedure. Fifty patients were randomly allocated to receive an i.v. infusion of 100 ml saline, with 100 mg tramadol or alone, before endoscopy. At the end of the procedure patients were asked to score the discomfort experienced and to give an exam evaluation. The endoscopist also analyzed his performance. Tramadol patients reported a pain score of 39 ±10 (mean ±SE), compared to 45 ±8 for the placebo group (P=0.25); the evaluation of endoscopy was also similar (tramadol, 66 ±12; placebo, 70 ±9; P=0.15). The endoscopist also reported a similar score (65 ±4 after tramadol; 69 ±4 after placebo; P=0.2). No significant sex or age related differences were detected. We conclude that tramadol, at least as a monotherapy, seems scarcely effective for controlling pain evoked by colonoscopy. Colonoscopy is often disturbed by poor patient tolerance; benzodiazepines or opiates are routinely used to overcome such problems, despite the possibility of undesired effects. Tramadol, an opiate analogue with potentially fewer side effects, has not been tested yet to this end. The aim of the study was therefore to evaluate the efficacy of tramadol as a premedication for the colonoscopic procedure. Fifty patients were randomly allocated to receive an iv infusion of 100 ml saline, with 100 mg tramadol or alone, before endoscopy. At the end of the procedure patients were asked to score the discomfort experienced and to give an exam evaluation. The endoscopist also analyzed his performance. Tramadol patients reported a pain score of 39 ± 10 (mean ± SE), compared to 45 ± 8 for the placebo group (P = 0.25 ); the evaluation of endoscopy was also similar (tramadol 66 ± 12; placebo, 70 ± 9; P = 0.15). The endoscopist also reported a similar score (65 ± 4 after tramadol; 69 ± 4 after placebo; P = 0.2). No significant sex or age related differences were detected. We conclude that tramadol, at least as a monotherapy, seems scarcely effective for controlling pain evoked by colonoscopy.