Background: Good reproductive health is a state of complete physical, mental and social well-being in all matters relating to the reproductive system. Human beings are beings, it means human beings are capable to reproduce and able to maintain reproductive health. Objective:  1. To assesses the existing knowledge regarding reproductive health among rural adolescent girls by giving pre-test. 2. To evaluate the effectiveness of constructive teaching program regarding reproductive health as measured by gain in posttest. 3. To find out an association between pre-test knowledge scores of rural adolescent girls regarding reproductive health with their selected demographic variables. Material and Methods: A study was conducted to assess the effectiveness of constructive teaching program on knowledge regarding reproductive health among 200 adolescent girls of selected rural PU colleges of Dharwad district. The research design used for the study was pre-experimental, one group, pre-test, posttest design. The demographic Performa were collected from the rural adolescent girls by using structured knowledge questionnaire. Data obtained in these areas were analyzed using descriptive and inferential statistics. Results: The study revealed that, the pre-test the knowledge scores of rural girls were 17% had good knowledge, 51% of them had an average knowledge and 32% of them had poor knowledge. Where as in regards with post test, 93% of them had an excellent awareness and 7% of them belonged to average and none of them had poor knowledge. The paired‘t’ value was 29.75* which was more than that of table value. Conclusion-So the study proved and concluded that the constructive teaching program was an excellent tool in improving the knowledge of rural adolescent girls.