The prevalence of symptoms of mandibular dysfunction was studied in 285 17-year-old adolescents living in the municipality of Skellefteå. They answered a questionnaire concerning general state of health and occurrence of headache, facial pain, or temporomandibular problems. A fifth of the subjects reported some symptoms involving the masticatory system. There was no statistically significant difference between sexes. Of the sample 13% had mild symptoms and 7% had severe symptoms of dysfunction. The most frequent symptoms were clicking sounds from the temporomandibular joint (13%) and a feeling of fatigue in the jaws (6%). Recurrent headache (once a week or more) was reported by 12% and appeared significantly more often among the girls (p less than 0.001). Three-quarters used both sides for chewing, and oral parafunctional habits were reported by 68%. Since mild and moderate symptoms of mandibular dysfunction and headache obviously make an early appearance, a routine dental examination should include screening of these symptoms to identify patients who should be observed more closely.