Birds killed by colliding with towers and windows were studied to describe the type and extent of injuries and, more precisely, to suggest the actual cause of death. A total of 502 specimens (247 tower kills, 255 window kills) were dissected, radiographed, and examined. Tower and window collision categories were further subdivided to consider age (subadult versus adult) and weight (<39 g, sparrow-size or smaller, versus > 39 g, cardinal size or larger) differences in injury and differential vulnerability. Injuries were classified as superficial, subdermal, or skeletal fractures. Comparisons of injuries between tower- and window-killed specimens indicate that the consequences of these two types of collisions are similar. Subdermal injuries were more severe in tower kills than in window kills. Subadults experienced more severe subdermal injuries than adult tower and window casualties. Among window kills, larger birds had more severe subdermal injuries than smaller birds. Collision victims may show blood or fluid in the mouth or nose cavities (30–60%), almost all have subdermal intracranial hemorrhaging (98–99%), and most lack any evidence of skeletal fractures (82–91%). Histological examination of the brain of two specimens revealed blood pools in the cerebrum and cerebellum. The extravascular bleeding in and around the brain is probably the actual cause of death in collision fatalities. Treatment to reduce brain edema if administered within 6–8 h shortly after impact can save some strike casualties.