Two hundred and forty subjects (113 boys and 127 girls), divided in three age groups, 7, 11, and 16 years were interviewed and clinically examined to estimate the prevalence of CMDs and the need for functional treatment, and to compare the functional status of the stomatognatic system in two subgroups: those judged to need orthodontic treatment and those judged not to need orthodontic treatment. Signs and symptoms of craniomandibular disorders were quite common and, in most cases, mild. There were significant differences in prevalence of CMDs between sexes. Only 3.7% of the patients were judged to need some functional treatment for CMDs. Trauma to the facial area and headaches were significantly associated with signs and symptoms of CMDs. No indication was found that oral parafunctions produce CMDs. No greater prevalence of CMDs signs and symptoms was found in subjects who needed orthodontic treatment than in subjects who did not need orthodontic treatment. In conclusion, preliminary results of this ongoing study support the contention that the high prevalence of signs and symptoms of CMDs is not really a measure of masticatory dysfunction, and that malocclusion does not appear to cause CMDs and/or to increase craniomandibular treatment need in a young population.