Concern over the complexity of the water method of colonoscopy insertion has dampened enthusiasm for its adoption. To compare the water method vs. air method in the hands of supervised trainees, a randomized, controlled trial was performed. Screening and surveillance colonoscopy patients consented to randomization. They all received minimal sedation for premedication. Colonoscopy was performed by supervised trainees. The primary outcome was pain during colonoscopy. During insertion the following parameters were significantly lower with the water method: pain scores and total doses or increments (fentanyl and midazolam) of medications. The above were accomplished without compromising unassisted or total cecal intubation rates, patient satisfaction scores at discharge and at 24 hours, patient willingness to repeat colonoscopy, or yield of adenomas. Predominance of male veterans was the main limitation. Supervised trainees replicated the superior performance of the water method reported for the attending staff confirming the water method is not difficult to learn.