Statement: A study to assess the effectiveness of structured teaching program (stp) on level of knowledge regarding aerobic exercise to prevent dysmenorrhea among adolescent girls in selected school at selected city. Objectives: 1.To assess the existing level of knowledge regarding aerobic exercise to prevent dysmenorrhea among the adolescent girls. 2. To assess the effectiveness of structured teaching program on level of Knowledge regarding aerobic exercise to prevent dysmenorrhea among the adolescent girls. 3. To find out the association between post-test level of knowledge score with their selected demographic variables. Research Methodology: Evaluative research approach was used with pre experimental one group pre test post test design population was 50 adolescent girls, non- Probability purposive sampling technique was used for data collection. Result: In the present study the pre-test- 12 (24%) had Poor knowledge, maximum 38 (76%) had Average knowledge and no one adolescent girls had Good knowledge regarding aerobic exercise to prevent dysmenorrhea. In the Present study the post test – maximum 48 (96%) adolescent girls were having adequate knowledge and no one adolescent girls were having poor knowledge and remaining 2 (4%) of adolescent girls were having Average knowledge regarding aerobic exercise to prevent dysmenorrhea. Conclusion: The study was drawn Percentage distribution of adolescent girl according to their level of knowledge showed they had average knowledge on aerobic exercise to prevent dysmenorrheal.