Functional infrared imaging has been used to study 17 patients, affected by myofascial pain, and 19 healthy subjects during maximal voluntary clenching (MCV). Aim of the study was to attempt to discriminate patients from healthy subjects through the analysis of the skin temperature distribution and its change during the clenching. The prestress and the post-stress temperatures were evaluated bilaterally for several regions of interest. We calculated differences in temperature between sides (DeltaTs) at each time (pre and post), and between times (DeltaTt) for each side (left and right). Subsequently, we compared DeltaTs and DeltaTt between the healthy and myofascial pain groups. DeltaTs was significantly higher in sufferers compared to healthy people (p<0.05) for both types of evaluation (by side and by time). DeltaTs was significantly different for masseter and sternocleidomastoid, whereas DeltaTt was higher in almost all sites (masseter, sternocleidomastoid, cervical and upper trapezius). Healthy subjects, undergoing MVC, showed the lowest DeltaT value variability, suggesting that temperature remained constant despite the induced physical exercise. Functional infrared imaging seems to distinguish healthy subjects from the patients suffering myofascial pain in almost all the investigated sites.