Aims: To assess the prevalence rates and risk factors of anterior disc displacement with reduction (ADDR) and symptomatic hypermobility in a large sample of children and teenagers. Prevalence rates were also established in samples of young adults and adults. Methods: Children from 7 Dutch primary and secondary schools (n = 1,833) aged 4 to 18 years (mean age ± SD 10.8 ± 3.9 years), 220 dental students aged 19 to 30 years (mean age ± SD 21.9 ± 3.6 years), and 100 dental school employees more than 30 years old (mean age ± SD 43.5 ± 9.8 years) were examined. The presence of ADDR or symptomatic hypermobility was scored using well-defined clinical criteria. For the children only, an additional standardized oral history and clinical examination were performed to assess possible risk factors. Odds ratios (ORs) were calculated with the use of logistic multivariate regression analysis. Results: The prevalence rate of ADDR in at least 1 of the 2 joints increased during childhood and adolescence and stabilized into adulthood at about 26.6%. In children and teenagers, besides age (OR = 1.06 for boys, OR = 1.23 for girls), risk factors for ADDR were a history of orthodontics (OR = 1.57), an increasing overbite (OR = 1.15), and protrusion (OR = 1.12). In children and teenagers, the prevalence rate of symptomatic hypermobility was higher for girls (13.8%) than for boys (8.2%). Besides gender (OR = 2.07), risk factors for symptomatic hypermobility were race (OR = 2.61 for non-Caucasians), masticatory muscle pain (OR = 1.95), and increasing maximum mouth opening (OR = 1.08). Conclusion: In children and teenagers, ADDR and symptomatic hypermobility have different prevalence rates and risk factors. Keywords: anterior disc displacement, prevalence rate, risk factors, symptomatic hypermobility, temporomandibular joint