To determine the effectiveness and associated side effects of a variety of bowel cleansing preparations before colonoscopy, 52 children, ages 4 months to 18 years, were evaluated. Data gathered included type of cleanout preparation used, adequacy of the preparations, and side effects. Twenty-two combinations of laxatives, lavages, enemas, and rectal suppositories were used. Side effects were reported in 90% of patients. In 79% of the patients the colon was clean or clean with some liquid feces, allowing a complete examination of the colon. Formed feces were present in 21 % of the subjects, and cleanout preparations were so inadequate in 9% of the subjects that the procedure had to be rescheduled. The most effective preparations were X-Prep liquid + Adult Fleet enema, GoLYTELY, and GoLYTELY + Adult Fleet enema, all of which allowed a complete examination of the colon. Pediatric Fleet ready-to-use enema was the least effective when used alone. X-Prep liquid + Adult Fleet enema caused the highest number of side effects (18%), while Pediatric Fleet ready-to-use enema alone caused the least (4%). The most effective cleanout preparation with the fewest side effects was GoLYTELY, used alone or in combination with enemas. These results suggest that many typical cleanout preparations yield inadequate results, wasting time or money, and argue in favor of the use of more effective preparations with fewer side effects, such as GoLYTELY.