BACKGROUND Effective solar protection is an uncommon practice among young people, increasing the likelihood of sunburn, sunstroke and skin cancers. This fact is more significant in the south of Brazil, where the prevalence of white skinned population is larger, being more prone to sun damage. OBJECTIVE To study the practices of sun exposure and sun protection in high school students from the city of Carlos Barbosa - RS. METHODS Cross-sectional study involving 775 students, enrolled on the first half of 2010, who had signed the consent form. We used a non-identifiable, self-administered questionnaire, with questions about related topics. Statistical analysis was performed using Chi-square or Fisher exact and t-Student tests. The study was approved by the Research Ethics Committee under the number 2010-115H. RESULTS Most students are exposed to the sun at the more critical periods, remaining exposed for more than an hour. Five hundred and seventy-six students (74,3%) reported using sunscreen, but less than 10% did it during all months of the year. Female teenagers are most likely to use sunscreen (p <0.001) and to spend less time exposed to sunlight (p <0.001). CONCLUSIONS Most high school students from Carlos Barbosa had unsuitable sun exposure and sun protection habits, characterizing a high risk behavior for skin diseases. The existence of public programs for clarification of the risks to the population and the subsidization of sun protection products were suggested by these young people.