The conventional total dose of 4 L of polyethylene glycol (PEG) given the day before the procedure is safe and effective. It has been the standard cleansing regimen for the last 25 years. To overcome the difficulty in completing the bowel preparation due to large volume and/or taste, reduced-volume (mixed) bowel preparation of bisacodyl and 2 L of PEG have been shown to provide adequate colon cleansing and better tolerability.