Background: Adolescence is defined as the teenage period of life, involving major biological changes and psycho‑social development. In adolescence, the girls first experience menstruation and good hygiene is essential during this period. Menstrual hygiene is an issue that is insufficiently acknowledged and has not received adequate attention in the reproductive health in developing countries. Aim: To elicit the knowledge, attitude and practice of menstrual hygiene in adolescent slum dwelling girls of Siliguri city. Subjects and Methods: A cross sectional, community based study was conducted in slums of Siliguri city of West Bengal and cluster sampling was used to select 798 post menarcheal adolescent girls residing in the slums. Data on knowledge, attitude and practices regarding menstruation were collected with the help of a pre‑tested and semi‑structured schedule. Simple descriptive statistics were used to analyse the data using SPSS 16 software (Chicago IL, USA). Descriptive statistics were applied to calculate proportion, mean and standard deviation and Chi square test was used to test the association between categorical variables and a P<0.05 was considered significant. Results: The knowledge of the respondents was assessed and it was found that only 23.4% (187 out of 798) knew about menstruation before menarche, whereas 653 out of 798 girls remarked sanitary napkins as the ideal absorbent. Regarding attitude towards menstruation, 55% of girls attributed menstruation as a debilitating event and 37.6% of them agreed that their periods resulted in no negative effect. When enquired about the menstrual practices 71.3% used sanitary napkins as absorbent material. Majority of the study participants had fair knowledge and practice about menstruation. Conclusion: The results of the present study highlights the fact that more efforts should be made to create awareness about hygienic practices during menstrual period, especially in underserved areas like slums.