The proposed clinical trial will evaluate the analgesic and adverse effects of duloxetine, a serotonin and norepinephrine reuptake inhibitor, in comparison to placebo in patients with temporomandibular joint disorder (TMJD). Duloxetine is approved as an antidepressant and has been shown effective in the chronic pain conditions of fibromyalgia and diabetic neuropathy. Decrease in pain and dysfunction and improvement in quality of life and global satisfaction will be assessed over 6 weeks. Successful demonstration of a therapeutic effect may provide a basis for clinical use of duloxetine in patients with painful TMJD.