Objective: Pain is major problem regarding quality of life in children undergoing tonsillectomy. Preemptive analgesia by medicine given before commencement of surgery is a new way recommended for relief of pain during and after operation. The purpose in this study to evaluate preemptive efficacy and safety of lower dose of tramadol, which was recently introduced in children undergoing tonsillectomy, Methods: This study was performed on 45 children undergoing tonsillectomy with or without adenoidectomy as a double-blinded trial, by using tramadol in two dosages (1 and 0.5 mg kg(-1)) and placebo. Pain assessment was done by facial pain score (FPS), visual analog scale (VAS) and postoperative analgesic requirement; further, duration of anesthesia and duration of awakening time, heart rate (HR) and mean arterial pressure (MAP) during and after anesthesia, postoperative nausea and vomiting (PONV) and recall of intraoperative events were recorded. Results: It was found that 73% children in placebo group needed analgesic medicine at the end of the first hour after operation, although no analgesic medicine was needed in tramadol groups (chi(2) test, P < 0.001). However, statistically significant decrease in FPS and VAS in tramadol groups were only found up to 15th and 30th min after operation, respectively (Kruskall-Wallis test, P < 0.05). On the other hand, intraoperative HR (10th, 20th and 30th min) and MAP (10th and 20th min) were found to be higher in placebo groups (ANOVA variance analysis, Tukey-Kramer test adjusted paired t-test, P < 0.001 and < 0.01, respectively). No significant difference was found in the other parameters, and no surgical complication and adverse side effect were occurred in this number of study sample. Conclusion: Tramadol in lower doses (0.5-1 mg kg(-1)) was an efficient preemptive analgesic that could be used at induction of anesthesia in adenotonsillectomies of children for providing both good analgesia during operation as supplementation to propofol anesthesia and postoperative analgesia in only early period. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.