Stress-induced muscle hyperactivity has been proposed as a major aetiological factor in the production of pain in the muscles of mastication and the temporomandibular joints. In the present study, a total of fifty-two patients with joint or muscle pain were evaluated for stress with the Derogatis Stress Profile (DSP). The muscle pain group (n = 24) had higher clinician ratings of psychological factors, stress and chronicity. The muscle-pain group also had higher Environmental Stress scores on the DSP, more intense pain, and more activity impairment than the joint-pain group (n = 28). The results of multiple regression analysis suggest an association between pain, depression, and impairment of activity in the muscle-pain group but not in the joint-pain group. The overall results further suggest that muscle pain develops at 'normal' levels of stress.