Objective The objective of this study was to assess temporomandibular joint (TMJ) abnormalities in juvenile idiopathic arthritis (JIA) by longitudinal radiographic examinations from childhood to adulthood. Study design Radiographic TMJ evaluations of 60 JIA patients were obtained at baseline (mean age 8.6 years, mean disease duration 3.2 years) and 1 to 3 times thereafter, with the final examination on average 27 years after baseline. A radiographic grading system for severity of TMJ abnormality was applied. Results Cumulative radiographic TMJ abnormalities increased from baseline to final examination (42% to 75%, P < .001), as did bilateral TMJ involvement (60% to 82%, P < .001). Of patients with TMJ abnormalities, 53% showed progression, and 16% revealed signs of improvement. TMJ abnormalities were associated with physical limitations at baseline and reduced well-being and more extensive joint involvement at the final examination. Conclusion The frequency of TMJ abnormalities in JIA was high and increased from childhood to adulthood. Although progression of TMJ abnormalities was the general rule, near normalization also occurred on occasion.