This investigation analyzed the influence of orthodontic treatment performed in childhood on the long-term development of signs and symptoms of temporomandibular disorders (TMDs). The original sample consisted of 50 consecutive patients (27 girls and 23 boys) with different morphological malocclusions, who were to receive orthodontic treatment. Their mean age at start of treatment was 12.9 years. Seventeen (range 15-18) years after completion of orthodontic treatment, 40 former patients (89% of the traced subjects) completed and returned a questionnaire, and 31 subjects (69% of the traced subjects) were also examined clinically. A great majority of the participants were pleased with the result of the orthodontic treatment. Relapses of morphological malocclusions were very uncommon. The prevalence of signs and symptoms of TMD was low both before and after the active phase of orthodontic treatment, as well as at the long-term follow-up after 15 to 18 years. The incidence per year of manifest TMD requiring treatment was approximately 1%. The result of the present investigation supports the opinion that orthodontic treatment in childhood does not entail an increased risk to develop either signs or symptoms of TMD later in life.