Aims: To prospectively evaluate the effectiveness of a treatment regimen comprising counseling and physical therapy in patients with myofascial pain of the masticatory system, and to explore whether the duration of the physical therapy offered (4 vs 6 weeks) would influence the treatment result. Methods: Twenty-six patients were randomly distributed over 2 groups. All patients received reassuring information, advice regarding relaxation of the jaws, avoiding parafunctions, and limited use of the jaws. In addition, a physical therapy program (heat application, massage, ultrasound and muscle stretching) was initiated 2 weeks after the start of the study (group I, receiving 4 weeks of physical therapy) or immediately from the start of the study (group II, receiving 6 weeks of physical therapy). The following parameters were taken at baseline, 2, 4, and 6 weeks: visual analog scale (VAS) scores of present pain; lowest and highest pain over the past period; percentage of pain relief; jaw function assessment by the Mandibular Function Impairment Questionnaire (MFIQ); and pressure pain thresholds (PPTs) of the masseter, temporalis, and thumb muscles. Statistical analysis used a linear mixed model and corrected for multiple testing (Tukey test). Results: Pain and MFIQ scores decreased while PPTs increased in both groups. Only after 4 and 6 weeks, significant differences were present for the PPT of the masseter in group I (P < .02) and the temporalis in both groups (P < .01). Also, the VAS scores of present (P < .02), minimal (P < .01), and maximal (P < .0001) pain and the MFIQ score (P < .001) improved. After 6 weeks, a mean of 60% pain decrease was reported (P < .0001). There were no significant differences between the groups receiving 4 weeks vs 6 weeks of physical therapy. Conclusion: A conservative approach involving counseling and physical therapy resulted in significant improvement in parameters of pain and jaw function in patients with myofascial pain. A controlled study will be necessary to elucidate the specific effectiveness of physical therapy over counseling or no treatment. J OROFAC PAIN 2003;17:42–49.