ABSTRACT Adolescence is a transition period from childhood to adult life. During this period, pubertal development and sexual maturation take place. There is a substantial lacuna in the knowledge of menstruation and menstrual hygiene among adolescent girls. Adolescent girls are often reluctant to discuss this topic with their parents, friends, or anyone. This in turn leads to ignorance of the scientific facts and hygienic health practices among adolescent girls. Better knowledge and safe menstrual practices will avoid risk against reproductive tract infections and their consequences. With this scenario, it would be appropriate to give educational intervention to girls at the school level itself. Therefore, increased knowledge about menstruation right from childhood may escalate safe practices and may help in mitigating the suffering of millions of women. Objective: The study was conducted to assess the effectiveness of a planned teaching program on knowledge regarding menstrual hygiene among high school adolescent girls in selected schools of Damoh. Setting: The study was conducted in selected schools of Damoh. Design: A pre-experimental one-group pre-test post-test design was used. Sampling technique: The samples of this study are selected by using a nonprobability non-probability purposive sampling technique. Sample: The sample for the present study comprises 218 adolescent girls from selected high schools in Damoh. Tools for data collection: The structured questionnaire was used as an instrument to measure the level of knowledge regarding menstrual hygiene among adolescent girls. Finding & Results: The finding of pre-test data Scores showed that the majority 77% of adolescent girls had inadequate knowledge and 20% of the sample had moderate knowledge 3% had adequate knowledge. Findings of post-test data showed that the majority 85% of the sample had adequate knowledge and 10% of the sample had moderate knowledge and 5% had inadequate knowledge. The mean post-test knowledge score (30.73) also was higher than the mean pre-test score (13.34). The comparison of pre-test and post-test knowledge scores of adolescent girls shows the obtained value of 35.72 is greater than the table value at 0.05 (2.32) level of significance. Therefore “t” valve is found to be signs indicating that there is a significant difference between pre-test and post-test knowledge of adolescent girls. A Chi-square test was calculated to find out the association between the demographic variables and the level of knowledge regarding menstrual hygiene among adolescent girls of selected high school adolescent girls of Damoh. The findings indicates that all the variables such as Age (χ 2 =2.69) Educational level (χ 2 =5.45), Religion (χ 2 =10.57) Family type (χ 2 =6.91), Mothers Education (χ 2 =2.90), Income of Family (χ 2 =3.64) Age of menarche (χ 2 =2.35), Source of information (χ 2 =4.10). Only in Religion, Family Type calculated P<0.01 were found to be significant at 0.05 level of significance. Thus it can be interpreted that there is no significant association between pre-test levels of knowledge among adolescent girls with their selected demographic variables. Conclusion: The study concluded that the PTP on Menstrual Hygiene was an effective method for providing moderate to adequate knowledge and help adolescent girls to adopt healthy lifestyles and to enable them to live a better quality of life by saving guarding against the effects of poor Menstrual Hygiene. Keywords: effectiveness, Knowledge, planned teaching program, menstrual hygiene, and adolescent girls