The present investigation of a relatively large Danish sample of patients with Juvenile Chronic Arthritis (JCA) revealed high frequencies of symptoms from the masticatory apparatus. 63% of the patients had destructive changes in the region of the mandibular condyles caused by arthritis. In one third of these cases the destructions were severe. Three fourth of the patients with TMJ-affection showed bilateral affection, and one fourth had unilateral affection. TMJ-affection was positively correlated to the duration and the severity of the general disease at the time of examination. Fifty per cent of the patients with TMJ-affection had reduced mouth opening capacity and most of these patients were aware of the problem themselves. The frequency of other symptoms from the TMJ and the jaw musculature was relatively high in the patient group. However, there were no significant differences between these frequencies when the group with TMJ-affection was compared to the group without TMJ-affection except for mouth opening capacity. The patients with TMJ-affection had significantly higher frequencies of frontal and lateral open bite and midline devition when compared to the patients without TMJ-affection. Furthermore, the patients with TMJ-affection had a significantly higher frequency of crowding in the mandibular incisor region than the patients without TMJ-affection. Thus, the study showed that TMJ-affection is common among children with juvenile chronic arthritis, and that the TMJ-affection may result in both functional problems and malocclusion.