AIMS: To develop and test a biopsychosocial model using structural equation modeling for predicting orofacial pain symptoms in a sample of patients with masticatory muscle pain (MMP). METHODS: Data were collected from clinic records of 251 adult patients who presented for initial evaluation to the Orofacial Pain Center at the University of Kentucky College of Dentistry and were subsequently diagnosed with MMP. Data were used to fit a model relating stressors, psychological distress, arousal, sleep problems, oral parafunction, and pain symptoms. Items from the Multidimensional Pain Inventory (MPI) and the IMPATH:TMJ, a comprehensive biopsychosocial assessment of patients with temporomandibular disorders (TMD), were used to construct a measurement model of five latent variables. RESULTS: Estimation of the model indicated a good fit to the data and significant associations between stressors, psychological distress, arousal, sleep problems, and pain symptoms. Sleep problems partially mediated the relation between arousal and pain symptoms. Contrary to hypotheses, no association occurred between oral parafunction and pain symptoms, possibly indicating that any relationship between oral parafunction and pain symptoms may not exist. CONCLUSION: Results from the model tested in the present study are an additional step toward developing a more comprehensive biopsychosocial model explaining the nature and etiology of MMP in orofacial pain and TMD. With additional development and testing, it may also serve as an aid to planning interventions, especially psychosocial interventions targeting stress management, psychophysiological regulation, psychological distress, and sleep problems.