Aims: To determine the prevalence of treatment need for temporomandibular disorders in adult populations by meta-analysis of nonpatient studies and to investigate factors influencing temporomandibular disorder treatment-need estimates. Methods: Population-based and nonpatient studies of adult subjects with temporomandibular disorders published in the English language prior to July 2006 were systematically reviewed. Electronic databases (MEDLINE, CINAHL, and Science Citation Index Expanded) were searched (n = 641). To combine data, fixed- and random-effects meta-regression models were used. Subgroup analyses were performed to assess factors influencing treatment need estimates. Results: Of 676 articles identified, 17 (9,454 subjects) met the study criteria. The prevalence of treatment need for TMD in adults (95% confidence interval) was estimated to be 15.6% (10.0, 23.6) for the fixed effect model and 16.2% (11.2, 21.1) for the random-effects model. Criteria of estimating treatment need and place of study strongly influenced summary estimates of treatment need (P .001). Need estimates derived from clinical TMD signs were higher than estimates based on subject-reported symptoms (P = .010). Estimates for younger subjects (19 to 45 years) were higher than for older subjects (46+ years; P = .013). Conclusion: The treatment need for TMD in the general adult population is substantial and varies according to definition, criteria, and age. Findings of this meta-analysis can be used for planning and allocating health-care resources. Keywords: epidemiology, temporomandibular disorders, temporomandibular joint dysfunction, treatment need