PURPOSE: The objective of this study is to show how baseline findings can redefine the design of an intervention. DESIGN: A baseline cross-sectional study. Setting. The study area was a suburban community near the Nicaraguan capital, Managua. SUBJECTS: A sample of 612 girls aged 10 to 14 years was selected, and 592 (97%) participated in the study. MEASURES: Using individual interviews, data were collected on sociodemographics; self-esteem and life prospects; gender; sexuality and human reproduction; knowledge of sexually transmitted diseases, human immunodeficiency virus, and acquired immunodeficiency syndrome; violence; and networking. ANALYSIS: Frequency tables. RESULTS: A high proportion (87.5%) of the girls lived with their mothers, and only 59% had their fathers living with the family. In 51% of the sample, the mothers made the decisions at home. For the majority of the girls, their mothers were their referent persons when they wanted to talk about sexuality and pregnancies, whereas only a few girls said they would talk with friends. CONCLUSION: The mother is the most important significant other, and thus, according to the theory of reasoned action, she would be the most important person to influence the girl. Careful investigations into which groups are forming the norms are essential for an effective intervention program in order to change behavior and enhance self-esteem.