Part 2 of our study evaluated the effect of artificial grass on the athletes that play on it. In this section we have reviewed the epidemiological studies that have evaluated the influence that artificial grass has on the frequency and site of injury to American football players. From this review we have concluded that play and practice on an artificial surface is probably responsible for an increase in the relative risk of injury to the lower extremity of the participants. However, it is evident that more well controlled studies are necessary to completely clarify this issue.