This study estimates the prevalence of the myofascial subtype of temporomandibular disorders (M-TMD) defined by Research Diagnostic Criteria (RDC), and relates that prevalence to the surveyed report of facial pain. From among 20 000 women selected at random in the NY metropolitan area who completed a telephone survey of facial pain, 2000 were invited for an RDC/TMD examination; 782 examinations were completed. Prevalence was estimated in analyses that were weighted to correct sampling biases. Differences among demographic strata were evaluated with logistic regression. The prevalence of M-TMD was estimated to be 10.5% (95% CL = 8.5-13.0%). Prevalence was significantly higher among younger women, among women of lower socio-economic status, among Black women, and among non-Hispanic women. The report of facial pain in the telephone survey (10.1%) had high specificity for M-TMD diagnosis (94.7%), but low sensitivity (42.7%). M-TMD is a fairly common disorder among American women. Among those reporting facial pain during the last month, half met RDC palpation criteria for M-TMD; thus, a formal physical examination is imperative to establish this diagnosis. Prevalence varies with age, socio-economic status, race and Hispanic ethnicity. A substantial number of RDC-diagnosed cases of M-TMD did not report facial pain in the survey; the reason for this requires further study.