Objective: Habituation has an important role in attention. By reducing one's sensitivity to a constant source of stimulation, it frees up attention resources to process new distinct items. Impaired habituation may disrupt sustained attention via inability to modulate the repeated intrusion of irrelevant stimuli. Method: Using Troxler fading, this study investigated habituation to peripheral stimuli in adults with ADHD. A total of 41 adults (21 ADHD and 20 controls) participated in the study. Results: Adults with ADHD were slower to habituate to peripheral stimuli. Conclusion: The findings suggest that impaired habituation may explain the clinical symptoms associated with adult ADHD. (Contains 5 tables.)