Adolescence is marked by profound biological and psychological changes. However, adolescent health, especially reproductive health, is a neglected area. The study aim was to recognize the perception of adolescent girls regarding the sexually transmitted diseases. A descriptive cross-sectional study design was used to conduct the study in three governmental secondary schools for girls in Benha city. It included 420 secondary school girls selected by random sampling technique. The data were collected using a self-administered questionnaire including knowledge and attitude rating scale. The study results revealed that the highest levels of satisfactory knowledge were related to anatomy of reproductive system (73.8%), and female genital mutilation (73.6%), while only 29.0% were had unsatisfactory knowledge about sexually transmitted diseases. The sources of information were mainly the school (74.0%), and mass media (48.1%). Overall, 52.1% of the students had total positive attitude. Knowledge was significantly higher among students in urban areas (p