This study seeks to better understand the impact of practice-level factors on up-to-date (UTD) rates in children. We compared practice-level vaccination rates for 54 practices to survey data regarding office practices for staffing, vaccine delivery, reminder-recall, and quality improvement. Vaccination rates at 24 and 35 months were analyzed using t tests, analysis of variance, and linear regression. Private practices and those using standing orders had higher UTD rates at 24 months ( P = .01; P = .03), but not at 35 months. Having a pediatrician in the office was associated with higher UTD rates at both 24 and 35 months ( P < .01). Participating in a network and taking walk-in patients were associated with lower UTD rates ( P = .03; P = .03). As the percentage of publicly insured patients decreases, the UTD rate rises at 24 and 35 months ( r = -0.43, P = .001; r = -0.037, P = .007). Reported use of reminder recall-systems, night/evening hours, and taking walk-in patients were not associated with increased UTD rates.