Collegiate American football injuries for two year seasons in Japanese Kansai Division I team were analyzed using injury rates (IR) per 1000 athlete-exposures (1000AE: one athlete-exposure was defined as a player participating in one game or one practice.), especially focusing on lower limb injuries. The overall game injury rate (GIR: 38.3) was significantly higher than practice injury rate (PIR: 13.1) (X²=12.355, p < 0.05). The difference between GIR in 2008 season (50.8) and in 2007 season (25.7) was significant (X²=8.235, p < 0.05). The lower extremity injuries approximately occupied 60% of all injuries, especially GIRs of both ankle inversion sprains (3.8) and anterior cruciate ligament (ACL: 3.3) injuries being much higher. PIR in this study was higher than the rates of collegiate American football teams in the U.S.A., especially PIRs of knee ligament injuries (ACL and medial collateral ligament injuries) and ankle sprains (inversion and eversion sprains) being much higher. Regarding the occurrence of injury, GIR with contact in ACL injuries (2.8) and GIR without contact in ankle inversion sprains (2.4) were the highest. It is also necessary to change practice plans and circumstances so that the PIR of knee and ankle injuries could be reduced. Research is needed on injury prevention for knee and ankle injuries in the games and practices.