Rationale Midazolam is known for its safety, effectiveness for procedural sedation during gastrointestinal (GI) endoscopy and is used as standard sedative by endoscopists worldwide. Remimazolam is a novel, recently approved sedative, with the potential to facilitate a faster (neuropsychiatric) recovery. Therefore, it may potentially enable earlier discharge and improvement of post-procedural memory compared to midazolam. Furthermore, remimazolam may enhance patient satisfaction. Objective The investigators aim to compare the use of remimazolam and midazolam for sedation during diagnostic upper GI endoscopies in a randomized clinical trial. Main trial endpoints Time to full alertness (time interval from the last dosage midazolam or remimazolam to the first of 3 consecutive MOAA/S scores of 5). Secondary trial endpoints Interval between arrival in the recovery room and full alertness, patient satisfaction (based on questionnaire after discharge and after 1 day), duration of amnesia (based on memory test after 1 day), time interval between last dosage of sedative and readiness for discharge (first Aldrete score of at least 9), total dosage and number of boluses for adequate sedation, time interval between first dosage of sedative and start of the procedure, endoscopist satisfaction (scored 0-10 after the procedure). Trial design Randomized, multicenter, double blind, clinical trial, which will take 2 days for study participants. Trial population Adult patients scheduled for diagnostic upper GI endoscopy with sedation. The anticipated use of fentanyl or other opioids during endoscopy is an exclusion criterium (n=148 patients). Interventions Participants will be randomly assigned to receive either remimazolam or midazolam as a sedative and will be followed up until one day after the procedure. One group will receive midazolam as a sedative, and another group will receive remimazolam as a sedative. Both agents will be administered in accordance with current guidelines. Vital signs, MOAA/S scores, and Aldrete scores will be monitored. Additionally, a memory test and a questionnaire will be administered to the participants. Ethical considerations relating to the clinical trial including the expected benefit to the individual subject or group of patients represented by the trial subjects as well as the nature and extent of burden and risks This study aims to evaluate two procedures employed in regular daily care. Both sedatives used in this study are considered safe and effective for procedural sedation. Therefore, the investigators anticipate minimal risk for the participants involved in the study. Participants will not be subjected to any additional interventions or hospital visits apart from randomization, data collection, and two short questionnaires to evaluate amnesia and patient satisfaction. There will be no direct benefits for the participants as a result of their participation in this study.