Adequate colonic cleansing is essential for accurate and safe colonic procedures. Common preparations for cleansing include diet in combination with a cathartic agent, gut lavage, and phosphate preparations. The diet used with a cathartic consists of clear liquids or is designed to leave a minimal colonic fecal residue with laxatives. Gut lavage solutions wash out the colon in a safe and effective manner. Phosphate preparations offer an attractive alternative due to smaller volumes required for ingestion; however, electrolyte disturbances can occur. This review discusses the development and clinical experience with various colon cleansing regimens and efforts to improve the tolerability and safety of preparation for colonoscopy, virtual colonoscopy, colon surgery, barium enema, and flexible sigmoidoscopy.