Treatment of the trigger points(TrP) is the most important thing for management of myofascial pain syndrome(MPS). The most effective treatment of TrP is local injection with various types of drug or dry needling, but the effectiveness of each drug was not the same by each investigator. The purposes of this study are to evaluate diagnostic value of Digital Infrared Thermographic Imaging(DITI) for trigger points and therapeutic effects of lidocaine and normal saline by DITI. This study included 15 patients who have TrP on upper trapezius muscles as a patient group and 10 normal adults as a control group. 2 cc of 2% Lidocaine was injected to the TrP of upper trapezius muscles in a patient group and to one side of upper trapezius muscles in a control group. One week after the first injection, 2 cc of normal saline was injected by the same method in a patient group. DITI was taken sequentially, preinjection(Pre), immediately after injection(P0), 15(P15), 30(P30), 60(P60) minutes and 24 hours(P24h) after injection. The parameters, temperature difference(ԤT) of both sides, changes of ԤT(ԤdT), visual analogue scale(VAS) were recorded at each point. It was considered abnormal, when the ԤT was above 0.6^oC. The patient group was subdivided as Group I(hot spot), Group II(cold spot) and Group III(no difference) according to preinjection thermographic findings of TrP. The results were as follows: 1) ԤT of control group was within 0.52^oC(95% confidence interval), 2) the numbers were 9 in Group I, 3 in Group II and 3 in Group III, and the sensitivity and specificity of hot spots for MPS were 81.8% and 57.1%, respectively, 3) ԤT was more reduced after lidocaine- than normal saline-injection, 4) VAS was more reduced after lidocaine- than normal saline-injection, especially in Group I and II. It is concluded that DITI can be used as one of the diagnostic tools for TrP and lidocaine is more effective than normal saline for the treatment of TrP.