Published guidelines for timing of follow-up colonoscopy assume that the entire colon mucosa is visualized and provide no guidance in the case of poor preparations. We aimed to determine how preparation quality during screening colonoscopy affects gastroenterologists' recommendations on the timing of follow-up colonoscopy. Gastroenterologists were shown representative images of four colonoscopies with differing colon-preparation quality. For each set of images they were asked to recommend when a hypothetical patient with no polyps or malignancy on screening examination should return for a subsequent colonoscopy. For the same patient, gastroenterologists were asked to give recommendations based on a preparation-quality grading scale. The survey was completed by 239 gastroenterologists. Nearly all recommended 10-year follow-up colonoscopy for the best-appearing preparation. For the three imperfect preparations there was considerable variability in recommendations; follow-up timing ranged from 1-2 days to 10 years for identical preparations. Similar variability was seen in recommendations based on a preparation-quality grading scale. Endoscopists generally recommended progressively shorter-interval follow-up as colon preparation worsened, with median recommended follow-up of 10, 5, 1, and 0.25 years for the four sets of images. No association was seen between personal demographics or practice characteristics and follow-up recommendations. When colon preparation is imperfect, gastroenterologists provide highly variable recommendations regarding timing of follow-up colonoscopy.