The authors made a survey in order to evaluate the young students' knowledge about Sexually Transmitted Diseases. It was carried out duringone Health and Nutrition Exposition, prepared specially for these students of Ribeirão Preto. 924 people - over 12 years old, female and male participated in our study; and they were from various socio-economic classes and different school levels. In this study, they could observe that many students know nothing about such diseases, and others have incorrect ideas about them.