In Guatemala, around 28 percent of young women become mothers before their eighteenth birthday. In other Latin American countries for which we have comparable data, the percentages range from 26 percent in El Salvador to 14 percent in Brazil. Combining these data with what we know about age-specific fertility rates-Guatemala trails closely behind El Salvador-and Honduras with the third highest age-specific fertility rate for 15- to 19-year-olds in Latin America-we may infer that Guatemalan females are among the most likely in both Central America, and in the entire Latin America region, to make an adolescent transition to motherhood. Drawing on data from nine Demographic and Health Surveys, this paper offers two complementary explanations for Guatemala's relatively high level of adolescent motherhood. First, Guatemalan females are more likely thars women in the comparison countries to be exposed to the risk of motherhood during adolescence. This is because of their earlier initiation of sexual activity combined with their lower levels of contraceptive use. Second, these adolescents tend to engage in sexual activity within the confines of marriage or a consensual union. This close coupling of sexual activity and union involvement means that Guatemalan women lack a major motivation to delay making art adolescent transition to motherhood: risk of out-of-wedlock childbearing. The coalescence of these factors is responsible for the situation in Guatemala where the proportion of young women having had sex within marriage by age 18 has remained virtually unchanged over the past 20 years. Until this group, which is responsible for the largest proportion of first births to adolescents, shrinks in number, the country is unlikely to witness a significant decrease in adolescent childbearing.