This invention relates to novel colonic purgative compositions of polyethylene glycol having an average molecular weight of at least 1,000 or at least 4,000. Further, this invention relates to methods of using the colonic purgative compositions. The formulations and methods of this invention are particularly useful to cleanse the bowel prior to diagnostic and surgical procedures and can also be employed in lower dosages as a laxative to promote elimination and/or to relieve constipation.