ObjectiveTo assess the relationship between real-world walking activity in children and adolescents with myelomeningocele (MMC) and gross measures of lower extremity strength, range of motion, demographics, and medical history. DesignProspective study. SettingParticipants recruited in outpatient clinics; data collected in a hospital-based motion analysis laboratory and in the community. ParticipantsChildren and adolescents (N=52) with daily step count data available from a larger study of ambulatory children and adolescents with MMC. InterventionsNot applicable. Main Outcome MeasureUnivariate and multivariate regression was used to assess which participant characteristics and clinical factors were related to average number of steps per day. ResultsUnivariate analysis showed a lower number of steps per day correlated with older age, male sex, higher body mass index, higher lesion level, use of assistive devices for ambulation, history of shunt placement, more television (TV) watched per week, lower hip extension and abduction strength, knee flexion strength, and ankle dorsiflexion and plantarflexion strength, and decreased knee and hip range of motion. Only assistive device usage and hours of TV watched per week remained in the final multivariate model predicting number of steps per day. ConclusionsWalking activity in children and adolescents with MMC was best predicted by assistive device use and amount of sedentary activity. Other predictors of walking activity from univariate analysis were related to assistive device use. This information can help tailor rehabilitation efforts and educate patients and families. Interventions targeting early prevention of strength loss and contractures may be important to retain or increase walking activity in children and adolescents with MMC.