The relationship between population density and the percentage of teens who electively terminate their pregnancy was the focus of this study. The United States population density was determined for each state and each district of the American College of Obstetricians and Gynecologists (ACOG) from the 2000 US Census. The United States teenage pregnancy statistics for females aged 15 to 19 years in 1999 and 2000 were obtained from the Alan Guttmacher Institute. The main measures were the correlation between population density and teen pregnancy rate or teen abortion rate by state and ACOG district. In 2000 there was no significant correlation between population density and the percentage of teenage females who conceived when analyzed by ACOG district (correlation coefficient r = 0.063, P =.87). In contrast, there was a significant correlation between population density and the percentage of pregnant teens who electively terminated their pregnancy when analyzed by ACOG district (r = 0.85, P =.003). In regions of greatest population density the percentage of pregnant teens who electively terminated was about 50%. In regions of least population density the percentage of pregnant teens who electively terminated was about 25%. Similar results were observed when teen pregnancy and abortion data from 1999 were analyzed. In the United States population density is not associated with the percentage of teenage females who become pregnant, but it is positively correlated with the percentage of pregnant teens that electively terminate their pregnancy. In areas of low population density teens who become pregnant may prefer birth to pregnancy termination. Alternatively, the access to pregnancy termination services may be suboptimal for teens in geographic areas with low population density. II-2