Adolescents are a heterogeneous group with diverse needs that vary depending on factors such as age, gender, marital status, place of residence and educational attainment. A healthy adolescence is the corridor to a healthy adulthood. Evidence suggests that adolescents continue to have a variety of unmet needs with reference to reproductive health. Objective: A descriptive, cross-sectional community based study was conducted among 22 adolescent girls situated in Chengalpattu. Knowledge related to puberty, menstruation & menstrual hygiene in the present study. Methods: Qualitative study was used to collect data. In depth interview and focus group discussion was conducted to collect the data. ID guides and FGD guides were used. Ten in depth interviews and two focus group discussion (6 respondents in each group) was conducted. Findings: Respondents were found to be in the age group between 13 yrs-18 yrs and the mean age was 15yrs. majority of the respondent associated menstrual cycle with impure blood, cleaning of body, unhygienic. None of the respondents were aware about the organ that was associated to menstrual bleeding and about the necessary for ovulation and neither were they using sanitary pads. All the respondents were aware of the physical changes that were associated with puberty. Majority (20) of the respondents expressed that their moments within and outside the house. They interaction with the male members of the house was also restricted. Majority of them had absented themselves from going to school due to the distance, lack of washroom and water facilities in the school. Conclusion: Knowledge on puberty, menstruation and menstrual hygiene is very essential for a healthy adulthood. This measure needs to be taken to impart knowledge and also to ensure that conducive environment is provided at school.