In this study, the effects of preoperative 900 and 1200 mg single dose of gabapentin on postoperative pain relief and tramadol consumption in elective open cholecystectomies were investigated. Fourty-five ASA I-II patients were randomly divided into three groups. Group I was control group and patients in group II and III received 900 mg or 1200 mg gabapentin 1 hour before the operations respectively. All patients received intravenous tramadol at the end of surgery via a patient controlled analgesia (PCA) device. Pain scores were evaluated at the recovery room (0),1, 2, 3, 4, 6, 8, 12 and 24h postoperatively at rest and movement, using a 10 cm VAS. In the recovery room, VAS scores at rest were three times less (1,4+/-0.6 versus 4,9+/-1.0 and 4.4+/-1.1), and visual analogue scale (VAS) scores at movement were two times less (3.4+/-1.0 versus 6.8+/-1.8 ve 6.1+/-1.6) in group III when compared to group I and II respectively. Mean loading doses were significantly lower in group III (28.3+/-8.7) than group I (66.6+/-20.4) and II (61.6+/-20.8). VAS scores at rest during the postoperative first 6h and at movement during the postoperative first 8h were significantly lower in group III than group I and II. Total tramadol consumption was lower in group III (240.4+/-31.0), than group I (456.0+/-35.5) and group II (438.7+/-35.0). Additional meperidine was necessary for two patients both in groups I and II, although none of the patients needed in group III. Higher patient satisfaction scores were obtained in group III. Adverse effect incidences were higher in group I and II than in group III. As a result, we believe that to improve analgesic quality after open cholecystectomy, preoperative single dose of gabapentin should at least be 1200 mg.