Purpose: Adequate colonic cleansing is essential for accurate and safe colonic procedures. Patient compliance is enhanced by simplicity and well-tolerated methods. Inadequate preparation of the bowel can result in both missed pathological lesions and cancelled procedures. We planned to prospectively (1) compare the efficacy of standard bowel preparation regimens like Golytely, Miralax, and Nulytely, and (2) the effect of liquid diet compliance, patient bowel habits and level of education on the quality of bowel preparation. Methods: Data was gathered on consecutive ambulatory outpatients presenting for colonoscopy who were randomized in chronological order to receive Golytely, Miralax, or Nulytely. Informed consent was obtained prior to data collection. Patients who were unable to give their own informed consent or unable to speak English were excluded from the study. Patient demographic, medical history, level of education, previous abdominal surgery, prior colonoscopy, bowel habits, compliance with liquid diet and bowel preparation regimen were noted. The endoscopist evaluated the preparation quality during the procedure using the validated Aronchick scale with 1 as excellent and 5 as inadequate quality. The data was analyzed by Student t-test, Chi square and ANNOVA tests as indicated using SPSS software version 15.0. Results: Total 157 patients included in the study, were divided into three groups (51 Golytely, 64 Miralax, 42 Nulytely). Mean age was 60 years (range 27 to 81). Gender: F76; M81. There was no statistically significant difference between the three groups in the quality of bowel preparation (P-value 0.861) or baseline characteristics including age, sex, race, level of education, co morbid conditions, prior abdominal surgery, prior colonoscopy, compliance with a liquid diet and bowel preparation compliance rates. However, more patients in Golytely group felt that it was more difficult for them to take the medication than to comply with a liquid diet (64.7% vs. 35.3%; P-value 0.0001 compared with other two groups). The main reasons for this were the large amount and the taste of the Golytely. In a separate analysis, patient's liquid diet compliance rather than bowel habit and level of education had a statistically significant effect on the quality of bowel preparation (P-value 0.0001). Conclusion: We did not find a statistically significant difference in the efficacy of Golytely as compared to Miralax and Nulytely. However, most patients found Golytely difficult to take due to the large amount and its taste. Moreover, patients' liquid diet compliance rather than perceived bowel habits and level of education better predicted bowel preparation quality.