The success and accuracy of colonoscopy is largely dependent on appropriate cleansing of the colon. The ideal bowel preparation should be safe, well-tolerated and effective. Although colonoscopy preparations are vastly better than the earliest barium enemas used in X-ray regimens, none of the currently available formulations sufficiently fulfills the above criteria. Currently used techniques of colon cleansing include dietary and cathartic methods, gut lavage and the administration of phosphates. All of these methods are efficacious, particularly when administered in a split dose (one the evening before and one just before the planned colonoscopy). Gut lavage methods are the safest method; however, dietary and cathartic methods are also reasonably safe. Low-dose phosphate preparations are well tolerated, but safety concerns have led to the withdrawal of some phosphate products from the US market. A new oral sulfate product that achieves a desirable balance of safety, tolerability in patients and efficacy will shortly be introduced. Physicians should be aware of the range of colonoscopy preparations available and their limitations, so that the best preparation can be chosen for an individual patient.