Open reduction and rigid internal fixation is the most popular treatment method for maxillofacial fracture patients, and it is unevitable that postoperative pain can be developed. Many surgeons including oral & maxillofacial surgeons have made constant efforts to decrease postoperative pain. This study is a comparison of postoperative analgesia and intramuscular analgesia in patients with mandibular fractures. In this study, twenty-one patients (Experimental group) were randomly selected and they were injected with IV patient-controlled analgesia (PCA; $Walkmed^{(R)}$, USA). For control group another twenty-one patients were injected with intramusclar non-steroid anti-inflammatory drugs ($Rheoma^{(R)}$, Samsung Pharm. Co.). And then, we measured visual analogue scale (VAS) scores from first postoperative day to second day at regular time interval. The following results were uptained; 1. In patient group who with open reduction and rigid internal fixation, there was significant difference of postoperative analgesic effect during the first postoperative day(p<0.05). 2. In patient group with over 90 minutes surgery time, there was significant difference of postoperative analgesic effect during the first and second postoperative day when compared between experimental group and control group(p<0.05). 3. In patient group with less than 90 minutes surgery time, there was no significant difference of postoperative analgesic effect during the first and second postoperative day when compared between experimental group and control group(p>0.05). 4. In patient group with surgery of open reduction using rigid internal fixation at single fractured site, there was no significant difference of postoperative analgesic effect during the first and second postoperative day when compared between experimental group and control group(p>0.05). 5. In patient group with surgery at two fractured sites, there was significant difference of postoperative analgesic effect during the first postoperative day when compared between experimental group and control group(p<0.05). As mentioned above, it suggest that patient-controlled analgesia is more effective for postoperative pain relief than intramuscular injection in patients with rigid internal fixation by open reduction after mandibular fracture occurred. Especially, it is considered that in patient with more than 90 minutes surgery time or in cases with multiple fractured sites had more effective results with PCA therapy than conventional intramuscular analgesics.