PURPOSE: Colonoscopy can be painful for patients and difficult for colonoscopists; however, it is hard to predict how painful or difficult the examination will be. This study was designed to identify factors that predict pain and difficulty during sedation-free colonoscopy. METHODS: A total of 848 consecutive sedation-free colonoscopies were evaluated in a prospective manner. Factors were recorded, including patient pain, intubation time, demographic data, history of abdominal surgery, bowel preparation status, diverticular disease, bowel habits, anxiety level, and number of previous colonoscopies. These factors were analyzed to determine their association with pain and difficulty. RESULTS: Almost all colonoscopies (845/848; 99.6 percent) were successful. Univariate analyses showed that lower body mass index, younger age, female gender, anxiety level, first time, intubation time, preparation status, previous hysterectomy, and previous gynecologic surgery were predictors of patient pain, and lower body mass index, female gender, anxiety level, preparation status, previous hysterectomy, previous gynecologic surge-ry, and constipation were predictors of difficulty of intubation. Multivariate logistic regression analyses revealed that lower body mass index, younger age, intubation time, preparation status, previous hysterectomy, and antispasmodic agent use were predictors of patient pain, and lower body mass index, female gender, constipation, preparation status, and previous hysterectomy were predictors of difficulty of intubation. CONCLUSIONS: By use of intubation time and patient pain, several patient characteristics were identified that may predict technical difficulty and pain associated with the procedure. These findings have implications for the practice and teaching of colonoscopy. PURPOSE: Colonoscopy can be painful for patients and difficult for colonoscopists; however, it is hard to predict how painful or difficult the examination will be. This study was designed to identify factors that predict pain and difficulty during sedation-free colonoscopy. METHODS: A total of 848 consecutive sedation-free colonoscopies were evaluated in a prospective manner. Factors were recorded, including patient pain, intubation time, demographic data, history of abdominal surgery, bowel preparation status, diverticular disease, bowel habits, anxiety level, and number of Previous: Colonoscopies. These factors were analyzed to determine their association with pain and difficulty. RESULTS: Almost all colonoscopies (845/848; 99.6 percent) were successful. Univariate analyzes showed that lower body mass index, younger age, female gender, anxiety level, first time, intubation time, preparation status, previous hysterectomy, and previous gynecologic surgery were predictors of patient pain , and lower body mass index, female gender, anxiety level, preparation status, previous hysterectomy, previous gynecologic surge-ry, and constipation were predictors of difficulty of intubation. Multivariate logistic regression analyzes revealed that lower body mass index, younger age, intubation time , preparation status, previous hysterectomy, and antispasmodic agent use were predictors of patient pain, and lower body mass index, female gender, constipation, preparation status, and previous hysterectomy were predictors of difficulty of intubation. CONCLUSIONS: By use of intubation time and patient pain, several patient characteristics were identified that may predict technical difficulty and pain associated with the procedure. These findings have implications for the practice and teaching of colonoscopy.