Infant walkers have been described as a cause of unexpected trauma in the first year of life. We conducted a prospective study to determine the mechanism and pattern of walker injuries presenting to an urban pediatric teaching hospital. We also studied the patterns of walker use. All injuries sustained by infants in baby walkers during a 1-year period were reviewed. The 139 injuries included 29 fractures. The most severe injuries were caused by falls down stairs; these falls accounted for 123 of the injuries. Stair gates were present in one third of all falls. At follow-up 2 months later, two thirds of the children had been in the walker subsequent to the injury. One third were still in the walker at 2 months after their initial injury. Less than half of the homes that had not had stair gates in place had acquired them at the time of follow-up. Baby walkers represent a cause of significant injury in the infant population; studies of warning labels and anticipatory guidance are needed.