There is no serious argument about the wounding potential of various kinds of penetrating projectiles. The laws of physics in concert with modern bullet testing have clarified and quantified the mechanisms by which bullets disrupt tissue. Despite this scientific background, much misinformation persists in the wound-ballistics literature. The article reviews the interaction of penetrating projectiles with human tissue. Understanding of wound allows the emergency physician to become a more informed reader of its literature, as well as a more reliable provider of care to the wounded patient.