Historically, research on pediatric pedestrian injuries has analyzed children younger than 5 years of age as a single group. However, in this study, these children were divided into two age groups which were reflective of differences in behavior and development. The data demonstrate differences in the circumstances of the pedestrian injury events between toddlers (0 through 2 years and ambulatory) and preschoolers (3- and 4-year-olds). Toddlers were more likely to be injured in nontraffic events whereas preschoolers were more frequently injured in traffic situations. A high proportion of toddler injuries occurred in residential driveways and were caused by vehicles backing up. The majority of preschoolers, often without supervision, were injured while crossing/darting midblock on residential streets near their homes. Reflecting these differences in circumstances and also developmental differences between toddlers and preschool children, there is a need for age-specific interventions to reduce pedestrian injuries in children younger than 5 years of age.