The term 'concussion' has been applied to head injuries of varying severity. Most studies have examined subjects suffering concussion of a severity requiring hospital observation, usually as a consequence of motor vehicle accidents. Milder concussive injuries such as those resulting from contact sport are often not reported in hospital-based studies. In this study, subjects with mild concussive injuries were studied with the aim of determining if neuropsychological sequelae are detectable. The subjects received their injuries while playing Australian Rules Football. Baseline pre-injury measures on the Paced Auditory Serial Addition Test PASAT, Digit Symbol Substitution Test DSST and Four-Choice Reaction time, involving measures of decision time DT and movement time MT, were obtained in a sample of 130 players. Ten players subsequently concussed were re-tested at 5 days post-injury. A control group of age-matched umpires were asssessed on two corresponding occasions. Analyses of covariance showed poorer performances following concussion on the DSST and DT measures. The results suggested that neuropsychological deficits are detectable after resolution of neurological symptoms in the early stages following mild concussive injury.