Objective: The aim of this study is to investigate the effects of bispectral index-controlled use of magnesium on propofol consumption, periprocedural hemodynamic response and patient comfort.Material: A total of 60 patients were enrolled in the study. In Group 1 (magnesium), a single dose 50 mg/kg magnesium sulfate diluted with 100 mL 0.9% NaCl was administered 10 min-utes before the beginning of the procedure. Initially bolus dose of 0.5 mg/kg propofol was ap-plied. The maintenance dose of propofol was 60 mcg/kg/min. During the procedure, the propo-fol infusion was increased by titration until the bispectral index (BIS) value of 70 was achieved. In Group 2 (saline), 100 ml 0.9% NaCl was administered 10 minutes before the beginning of the procedure. The bolus and maintenance doses of propofol, and target BIS values were the same as those in Group 1.Results: When BIS values were compared between the groups, the initial BIS values in the magnesium group (Group 1) were significantly higher than those of the saline group (Group 2) (p<0.05). The time to reach BIS 70 was significantly shorter in the magnesium group (p<0.05). Propofol consumption was greater in Group 2 than in Group 1 (p<0.05). The time to reach BIS 70 was significantly shorter in Group 1 (p<0.05). No significant difference was found between the groups in terms of patient- and endoscopist-satisfaction (p<0.05).Conclusion: The use of magnesium in addition to propofol may be an efficient and reliable op-tion to reduce the drug consumption during colonoscopic interventions.