OBJECTIVES: Chronic pain is one of the most common experiences of humans and a typical psychophysiological disorder. The aim of this study was to measure the psychophysiological responses in chronic pain patients using a biofeedback system, and to compare them with the results from normal healthy subjects. METHODS: Forty two patients with chronic pain (17 males and 25 females, average age 44.67+/-11.10 years) and 42 normal healthy controls (17 males and 25 females, average age 45.17+/-10.46 years) participated in this study. Electromyography (EMG), skin conductance (SC), and skin temperature (ST) were recorded using biofeedback system during the 3 phases (baseline, stress, and recovery) of stress reactivity test, and average values of them were calculated. Difference of values between two groups in each corresponding phase was analyzed with independent t-test, and change of values across phases of stress reactivity test was analyzed with paired t-test (all two-tailed, p<0.05). RESULTS: Compared to normal controls, chronic pain patients had higher value of EMG (baseline : 8.10+/-5.97 micronV vs 4.72+/-1.52 micronV, t=-3.56, p<0.01 ; stress : 11.25+/-6.89 micronV vs 8.49+/-4.78 micronV, t=-2.13, p<0.05 ; recovery : 7.12+/-3.77 micronV vs 4.78+/-1.59 micronV, t= -3.70, p<0.01) and SC (baseline : 1.06+/-1.0 micronS vs 0.42+/-0.29 micronS, t=-4.0. p<0.01 ; stress : 1.87+/-2.05 micronS vs 1.03+/-0.86 micronS, t=-2.47, p<0.05 ; recovery : 1.74+/-1.77 micronS vs 0.64+/-0.59 micronS, t=-3.8, p<0.01) in all the 3 phases. But, skin temperature comparison did not reveal significant differences in all the 3 phases between two groups. CONCLUSION: Psychophysiological responses of chronic pain patients in stress reactivity test were different from those of normal healthy controls. These results suggest that sympathetic nervous system is more activated in chronic pain patients.