Recently a non-electronic, disposable and portable infusor, Baxter $Infusor^{(R)}$, has developed for delivering not only a continuous drug infusion but also extradoses of medication on a demand basis. The present study examined the impact of two methods of pain management on recovery in 20 patients undergoing upper abdominal surgery for stomach cancer. One group, 10 patients, received IV meperidine in the recovery room and IM meperidine on the ward on a PRN basis(PRN group). In the other group, 10 patients, a loading dose of nalbuphine 0.1mg/kg was given when the patient first complained of pain in the recovery room and patient controlled analgesia with IV nalbuphine, 0.5mg/kg day for continuous infusion, was initiated and continued for 72 hours(PCA group). The devices for PCA group was Baxter Infusor with patient control module which had flow rate 0.5ml/hr and lockout time was 15 min. As results of this study, the patients of PCA group get less pain than PRN group on operation day, the first and second days after surgery. VAPS values are $6.47{pm}1.64$ vs $4.44{pm}1.38$, $5.02{pm}1.22$ vs $2.62{pm}0.93$ and $3.22{pm}1.47$ vs $2.02{pm}0.71$ respectively pertaining to PRN and PCA groups(p<0.05). In conclusion, PCA group with IV nalbuphine provided more effective postoperative analgesia than PRN group with conventional meperidine IM.