The purpose of this 20-year follow-up study was to assess whether pronounced morphologic traits of malocclusion, persisting from adolescence to about 35 years of age, imply an increased risk of persistent and severe mandibular dysfunction. In 1965-66 malocclusion was recorded in 176 adolescents; in 1981 these persons responded to a questionnaire concerning symptoms of functional disorders, and in 1986-87 malocclusion and signs of dysfunction were registered. Highly significant associations were observed between some of the self-reported symptoms and the signs registered 5-6 years later. Spearman correlation coefficients between the persistent traits of malocclusion, occurring at both examinations, and the signs of mandibular dysfunction were low in general. No association was found between the most severe and persistent functional disorders and any particular malocclusion. It is concluded that orthodontic screening of morphologic malocclusion in childhood would seem of limited value in attempts to predict mandibular dysfunction in adulthood.