Aim: To study the development over 20 years of signs and symptoms of temporomandibular disorders (TMD) in an epidemiologic sample and to analyze possible correlations between tbese signs and symptoms and some other variables. Methods: Tbe original group comprised 135 randomly selected 15-year-old subjects who were examined clinically and by means of a questionnaire for signs and symptoms of TMD. The examination was repeated after S, 10, and 20 years by the same metbods. After 20 years, when tbe original group bad reached tbe age of 35 years, 124 individuals (92%) could he traced, and they were sent a questionnaire and invited for a clinical examination. Tbe response rate was bigh: 114 subjects (92%) completed and returned the questionnaire, and 100 subjects (81%) attended the clinical examination. Results: There was a substantial fluctuation of both reported symptoms and clinically recorded signs over the 20-year period, but progression to severe pain and dysfunction of the masticatory system was rare. In botb the 15-year-old and 35-year-old subjects, 13% reported 1 or more frequent TMD symptoms. At age 35, only 3 subjects (3%) were classified as having severe or moderate clinical signs of dysfunction according to the Helkimo Index, fewer than in previous investigations. Women reported TMD symptoms and headacbe and had muscle tenderness and joint sounds more often than men. Correlations between tbe studied variables were mainly weak. Among the highest correlations found (r¡ = 0.4) were those between reported clenching and hruxing habits and TMJ sounds and jaw fatigue. Conclusion: In tbis epidemiologic sample followed from age 15 to 35 years, a substantial fluctuation of TMD signs and symptoms was found over time. Progression to severe pain and dysfunction was extremely rare. J OROFAC PAIN 2000;14;310-319 Keywords: bruxism, epidemiology, headache, orofacia! pain, temporomandibular joint