Bunk beds are commonly used in American households, yet to our knowledge, no studies have been done to determine if they are safe. We prospectively studied the incidence, epidemiology, and outcome of injuries related to bunk beds. We interviewed all patients with such injuries who presented to the emergency department between February 1987 and February 1988. A control group of children who use bunk beds but who came to the emergency department for another reason were also interviewed. There were 68 injured children and 54 controls during the 1-year study period. There were 47 injured children (70% of this group) and 26 control children (48% of this group) younger than 6 years, which is below the age recommended by the Consumer Product Safety Commission for bunk bed use. Carpeted floors were significantly more common in the control group, 67% (36 children) vs 42% (26 children). Injuries occurred most often when the child fell from the top bed (38 children [58%]), fell off the ladder (7 children [11%]), or fell off the bottom bed (8 children [12%]). Injuries occurred during sleep (19 children [29%]), getting in or out of the bunk bed (13 children [20%]), or playing in or near the beds (28 children [43%]). Of those injured while asleep, 13 of 19 children were younger than 6 years. Head injuries accounted for half the trauma (35 children [52%]), and extremities were involved in 16 patients [24%]. The most common injuries were lacerations (27 children [40%]) and contusions (19 children [28%]), but 8 children (12%) had concussions and 7 children (10%) had fractures. Six children (9%) required admission to the hospital. Head and face injuries were significantly more likely if the top bed had no side rails. These data suggest injuries could be prevented if side rails were mandatory for all top beds, young children were not permitted to sleep in bunk beds, and all children were encouraged not to use the beds for play.