To investigate associations between the number of physical activity facilities within walking distance of school and physical activity behavior in 12th grade girls during after-school hours. Girls (N=1394) from 22 schools completed a self-report to determine physical activity after 3:00 p.m. The number of physical activity facilities within a 0.75-mile buffer of the school was counted with a Geographic Information System. Associations between the number of facilities and girls' physical activity were examined using linear mixed-model analysis of variance. Overall, girls who attended schools with ≥5 facilities within the buffer reported more physical activity per day than girls in schools with <5 facilities. In addition, girls who attended rural schools with ≥5 facilities reported ∼12% more physical activity per day than girls who attended rural schools with <5 facilities. No difference existed for girls in urban/suburban schools with ≥5 vs. <5 facilities. When school siting decisions are made, the number of physical activity facilities surrounding the school should be considered to encourage physical activity in 12th grade girls. Copyright © 2011 Elsevier Ltd. All rights reserved.