ObjectiveTo identify an objective evaluation technique to guide return-to-play decisions following mild brain injury (MBI) using an agility task that incorporates cognitive and motor performance.DesignProspective, controlled, repeated measures study.SettingCollegiate athletic training facility.Participants84 athletes (25 male rugby players, 34 female rugby players, 25 male ice hockey players) from 3 intercollegiate club teams participated. 9 athletes who suffered MBI during their competitive seasons and 9 matched controls completed the entire study protocol.Main Outcome MeasuresTime to complete an agility task on the Cybex Reactor and a postconcussive symptoms scale score were assessed in all subjects during the preseason. Injured subjects and matched controls were also assessed 1, 3, 5, and 10 days postinjury.ResultsRepeated measures analyses of variance revealed significant differences between injured subjects and controls in postconcussion symptoms, but not agility performance. Post hoc testing revealed that injured subjects reported significantly more postconcussion symptoms on Day 1 after injury.ConclusionThe methods of agility assessment used in this study appear to not be sensitive enough to detect functional impairment following MBI.