Objective. We examined whether the anti-saccade task (AST) changes induced by the first methylphenidate (MPH) dose could be associated with subsequent clinical outcome in adults with attention-deficit/hyperactivity disorder (ADHD). Methods. Ninety-seven drug-naive DSM-5 ADHD adults participated in this study. The AST parameters were measured at baseline, after the first MPH-dose (10 mg orally), and 6 months after chronic MPH treatment. Results were compared with those of 50 healthy control (HC) subjects.