Objective: To determine if sensory overresponsivity (SOR) is a moderating condition impacting the activity of the Hypothalamic Pituitary Adrenal (HPA) Axis in children with ADHD. Method: Participants were children with (n = 24) and without ADHD (n = 24). Children in the ADHD group were divided into SOR (ADHDs) and non-SOR (ADHDt) groups using the Sensory Over-Responsivity Inventory. All children participated in the Sensory Challenge Protocol. Salivary cortisol was used as a measure of HPA activity. Two prechallenge and seven postchallenge samples of saliva were taken. Cortisol patterns between groups were examined using a mixed-effects ANOVA. Results: There was a borderline significant difference found between the ADHDt and ADHDs group (p = .056) and a significant difference between ADHDt and the typical group (p = .014). Conclusion: Preliminary results support the premise that SOR may be a moderating variable used to create subgroups in diagnostic populations such as ADHD. (J. of Att. Dis. 2010; 13(5) 468-478)