The objective was to analyze the structure of school blogs on sexuality and their utilization by adolescents. This quantitative, exploratory and documentary study was performed with 11 blogs designed by students and available online in March of 2012. The information was submitted to hypertext analysis and descriptive statistics, taking research ethics norms into consideration. Group and education blogs developed in Portuguese and Brazilian schools were most often signed by their authors and suffered few updates. The written posts mixed scientific and informal languages, besides presenting videos and images. Every blog included information regarding the number of followers, visits, comments and a contact to answer questions. The highlighted discussed topics were birth control methods and sexually transmitted diseases (STDs). Blogs are a resource for health education that should promote active discussions and rely on the participation of health care professionals.