Symptoms and signs of temporomandibular disorders were assessed in children enrolled in a randomized controlled trial of early treatment for Class II malocclusion. Children (mean age of 9.8 years) were assigned to a treatment protocol (bionator, n = 60; observation, n = 60; headgear/bite plane, n = 71) using randomized block stratification. Temporomandibular joint (TMJ) sounds, joint capsule pain to palpation, and muscle pain to palpation were scored as binary responses (present/absent in a subject). Determinations were made by blinded, calibrated examiners initially (DC1) and after a Class I molar correction was achieved or 2 years had elapsed (DC3). Univariate relationships among explanatory factors (group assignment, gender, age, time interval between DC1 and DC3, Class II severity, mandibular plane angle, preparatory treatment, whether Class I molar relation was achieved) and binary responses were explored using Chi square tables and ANOVA methods. Logistic regression modeled the relationship between binary responses and the explanatory variables. At DC1, the 3 groups were equivalent in the explanatory variables (P > .05). Subjects with a TMJ sound, joint pain, and/or muscle pain at follow-up were more likely those who had the sign at baseline (P < .01). Early treatment with bionators and headgear/bite planes did not place healthy children without these signs at risk for developing these signs. Only increasing age (for the development of sounds, P < .04) and failure to achieve a Class I molar relation (for development of muscle pain, P < .04) placed sign-free children at greater risk. Subjects with TMJ pain at baseline were 7 times more likely to have pain at follow-up if they had been treated with a headgear/bite plane or observed than if they had been treated with a bionator (P = .007). We conclude that an immediate benefit or risk for children receiving early Class II treatment with bionators and headgear/bite planes with respect to temporomandibular joint function does not exist with the prospect that Class II children with TMJ capsule pain may benefit from bionator therapy.