BACKGROUND The objective of this study was to determine if pre-operative oral midazolam administration decreased postoperative oral fluid intake after tonsillectomy with or without adenoidectomy. METHODS A retrospective chart review identified 104 patients who were undergoing tonsillectomy with and without adenoidectomy who were not given midazolam preoperatively and 182 who were given midazolam preoperatively. Indications for tonsillectomy with or without adenoidectomy included obstructive sleep apnea, recurrent acute streptococcal pharyngotonsillitis, and, in selected cases, periodic fever with aphthous stomatitis, pharyngitis and adenopathy. All patients were evaluated in the pre-operative area by the attending anesthesiologist, who then determined whether or not he/she felt the patient would benefit from premedication with oral midazolam prior to surgery. Patients whom the attending anesthesiologist judged would benefit from midazolam were then given a 0.12-1.06 mg/kg dose (mean 0.35 mg/kg, STD 0.12), at the discretion of the anesthesiologist. Various methods were used to perform tonsillectomy, such as coblation and electrocautery, at the discretion of the otolaryngologist. Results were not stratified by surgical technique. Oral fluid intake was calculated by establishing the time of return to the floor from surgery and determining the documented oral fluid intake for the next 12 h. Oral fluid intake per kg per hour was then calculated. The amount of midazolam given was documented. RESULTS There was no significant difference in oral fluid intake by group when adjusting for age and weight, F(1, 282) = 0.383, p = 0.537. Also, there was no significant difference in ml/kg/hr by group when adjusting for age and weight, F(1, 282) = 2.813, p = 0.095. CONCLUSIONS There was no significant difference in oral fluid intake between the no midazolam and midazolam groups, indicating that clinicians can continue to use their judgement in administering midazolam to select anxious patients prior to tonsillectomy with or without adenoidectomy. Future work could include multi-center retrospective reviews or a randomized placebo-controlled trial to examine more carefully the effects of midazolam on postoperative oral fluid intake. METHODS Level IV.