Baseball has one of the highest impact injury rates of all sports. These injuries are primarily attributed to impact by a ball after it has been hit, pitched or thrown. This paper will review the incidence and causal factors for impact injuries in baseball. Attention is given to the design and material properties of bats, in light of evidence suggesting balls hit into the infield from metal bats can reach velocities potentially lethal to defensive players. The distribution of bat mass along the long axis of the implement appears a major factor in the greater performance potential of metal bats over wooden bats of equal length and mass. The dynamic behaviour of baseballs has also been implicated in the severity of head and chest injuries experienced by players. Balls of greatly reduced stiffness have been introduced for junior play, but debate still remains over their performance and impact characteristics. The behaviour of the ball during high-speed impact with the bat has been the subject of relatively limited research, and the effect of manipulating baseball material properties to decrease batted-ball velocity is unclear. The value of batting helmets is evident in the observed reduction of head injuries in baseball, but the use of protective vests to decrease the incidence and severity of cardio-thoracic trauma appears to be contraindicated.