Postoperative pain following tonsillectomy remains a significant obstacle to speedy recovery and smooth convalescence. Inadequate analgesia causes poor oral intake and influences the length of hospital stay and ability to return to normal activity. Patient Controlled Analgesia (PCA) is a method of analgesia adminstration that consists of a computer driven pump with a button that the patient may press to adminster a small dose of analgesic drug. The aim of this study was to examine whether Intravenous Patient Controlled Analgesia (IV-PCA) can reduce postoperative pain after tonsillectomy. The 100 patients undergoing tonsillectomy with general anesthesia were divided into two groups. The PCA group patients (n=80) received a mixture of nalbuphine and ketorolac by Walkmed PCA infusor during first 48 postoperative hours. In control group (n=20), the patients received oral acetoaminophen (Tyrenol) regularly and tiaprofenic acid (Surgam) intramuscularly on a p.r.n basis. Analgesic efficacy was evaluated with visual linear analogue scale (VAS) and the adverse effects were evaluated with 4 point scale. The patients of PCA group had less pain than those of control group. The adverse effects in the PCA group were nausea and vomiting. This study suggests that IV-PCA may be safe and effective method of pain control after adult tonsillectomy and is better accepted than oral or intramuscular pain medications.