Objective: The Reliable Change Indexes (RCI) from the Immediate Post-concussion Assessment Testing (ImPACT) Test are used to inform return to play decisions. Previous research has found the RCIs to achieve an unacceptable false-positive rate between 22% and 38%. The current investigation examined RCIs in a sample of non-concussed athletes. Method: ImPACT data were collected pre- and post-season from 120 high-school and collegiate athletes. Athletes suffering concussion or with a diagnosis of Attention-Deficit/Hyperactivity Disorder were excluded (n = 5). Athletes were classified based on whether they exceeded at least one ImPACT cognitive composite or total symptom score (TSS) RCI (n = 59). Results: At least one significant RCI was achieved by 50% of the sample. These athletes tended to be male, younger, attend high school, and play either football or volleyball. A significant verbal memory RCI was most common (49%), followed by visual memory (25%), and reaction time (24%). ANOVA analyses controlling for age, high-school versus collegiate participation, gender, and sport found no group differences in pre-season composite or symptom scores; however, at post-season groups differed on the verbal, visual, and visual motor composite scales (p < .05–.01). Conclusion: Our results suggest that significant RCI scores are frequently achieved by asymptomatic high-school and collegiate athletes. Previous authors have suggested a significant RCI on the TSS and at least one cognitive composite should be considered as genuinely injured (Van Kampen et al., 2006). Applying this criterion to our sample, 7% would have been incorrectly classified. Implications for management will be discussed.