OBJECTIVE The major goals of analgesia and sedation are to provide pain control and anxiolysis and to facilitate therapeutic and diagnostic interventions. A combination of midazolam and an opioid is usually administered to achieve sedation and analgesia during colonoscopy. However, the value of adding analgesics to sedative agents has not been well evaluated. In this study, we compared the efficacy and safety of midazolam versus midazolam plus meperidine for colonoscopy. METHODS A total of 74 patients admitted for routine colonoscopy to our hospital between September 2008 and March 2009 were eligible for the study. The midazolam group received midazolam (n=34) and the midazolam/meperidine group received midazolam plus meperidine (n=40). Data regarding the procedure times, degree of pain (determined according to the standard visual analog scales and recovery time were collected. RESULTS There was no significant difference between the two groups with regard to the rate of inadequate bowel preparation. Mean visual analog scales scores were over three points and similar in the two groups. Recovery times (in minutes) were similar in the two groups (28.2 min, SD 5.3 for the midazolam/meperidine sedation group and 28.3 min, SD 5.4 for the midazolam group). The total procedure times were also similar in the two groups (mean 18.64 min, SD 6.7 vs 19.3 min, SD 10.1). There was no statistically significant difference between the two groups regarding the recovery time, procedures times and visual analog scales mean scores. CONCLUSIONS Patient safety, outcomes, and satisfaction are similar in colonoscopy procedures performed under sedation protocols using either midazolam and meperidine or midazolam alone. Although endoscopists favor the use of both medications together, adding meperidine to midazolam before the colonoscopy does not seem to have additive beneficial effect for the patients.