The aim of the study is to compare a new 2 litre bowel cleansing product versus a sodium phosphate solution already on the market. Efficacy of each bowel preparation, safety and acceptability will be assessed.

Multicentric (15 centres), prospective, randomised, single-blinded phase III pivotal study in patients undergoing a colonoscopy. Gut cleansing will be performed using 2 litres of NRL994 gut lavage solution with 1 litre (or more) of extra clear liquids or 2 x 45 ml of a sodium phosphate solution plus 2 litres (or more) of extra clear liquids the day before colonoscopy. Patients requiring a morning colonoscopy who fulfil the inclusion criteria, will be randomised. One of the two tested products will be delivered by a pharmacist, blindly from the gastroenterologist. The assigned product will be taken the day before the coloscopy according to the information leaflet. Efficacy of the two tested preparations will be measured on video-tape record of each colonoscopy by a final grading i.e. "the overall quality of colonoscopy prep" by an gastroenterologist expert. A standardised patient questionnaire administered by a nurse on the morning before colonoscopy will assess clinical tolerance and acceptability (satisfaction) of the prep. A baseline blood sampling will be withdrew before intake of the preparation and one more blood sample will be performed after the intake on the morning, before the coloscopy.

After the coloscopy, as the gastroenterologist gives the result of the coloscopy , a last visit is performed.

Inclusion Criteria:

• male or female, out and inpatients to be at least 18 years old and <75 years old sent to the endoscopic ward for diagnostic or therapeutic colonoscopy
• willing and able to complete the entire procedure and to comply with study instructions
• females of childbearing potential must employ an adequate method of contraception.

Exclusion Criteria:

• age <18 or > 75 years old
• ileus
• suspected intestinal occlusion or perforation
• toxic or congenital megacolon
• history of colonic resection
• patients with Crohn's disease or ulcerative colitis
• congestive heart failure NYHA III or IV
• documented renal insufficiency history with creatinine >170µmol/l
• known hypersensitivity to polyethylene glycols or Na phosphate and/or vitamin C
• concurrent participation in an investigational drug study or participation within 90 days of study entry
• females who are pregnant, or planning a pregnancy. Females of childbearing potential not using reliable methods of contraception
• subject has a condition or is in a situation which in the investigators opinion may put the subject at significant risk, may confound the study results, or may interfere significantly