This study compares the effects and probable complications of two groups of mix of propofol and fentanyle with mix of propofol and ketamin(called ketofol) in sedation in patients should be undergoing diagnostic colonoscopy.Inclusion criteria are: age over 18 years ;age under 80 years;and class 1 in American Society of Anesthesiologists(ASA).Exclusion criteria are: Coronary artery disease; Neurological and psychiatric disease;Egg sensitivities. 90 patients who should be undergoing diagnostic colonoscopy will enrolled in study.Our study will be done in Emam KHomeini hospital.We describe our purpose of research study for patients then after their satisfaction we will be included them in study.Their information about age,gender,past cardiac disease, etiology of colonoscopy,drug consumption will be collect in check list form.Incidently, patient will be divided to two groups,one will be received intra venous mix of propofol-fentanyle,dose of propofol is 0/75mg/kg and fentanyle 1ug/kg,and other group will be recieved intravenous mix of propofol and ketamine that named ketofol.Ketofol solution is made by mixing of 50 mg propofol and 50mg ketamine and 4 cc distilled water in a 10cc syringe.Second group will be received 0/75mg/kg ketofol. Patient sedation level will be differentiated by Ramsay sedation score and patient and physician satisfaction level will be differentiated by visual analogue scale(VAS).In both group sedation level before starting of colonoscopy should be above 5 in ramsay scale,if not, we inject 0/3mg/kg propofol to first group and 0/3 mg/kg ketofol to second group.Median recovery time,additional dose of propofol or ketofol,additional other sedative drug,and complications like vomiting,nausea,chilling,hypoxy,and complication of emergence of ketamin will be determined and compared in both group.