Context: Adolescents comprise one-fifth of India’s total population. There is widespread ignorance associated with unprotected sex, contraceptives, among young people. As majority adolescents in slum areas have illiterate and ignorant family backgrounds; they are misguided by the myths. Hence providing sex education for them is the need of the hour. Aims: 1) To assess the knowledge and awareness of adolescents in an urban slum area regarding some aspects of reproductive health. 2) To assess the need of sex education among them. 3) To study the impact of sex education on their knowledge Material and Methods: An interventional study was done on 132 adolescents of urban slum area, selected by simple random sampling. Informed consent was obtained from the participants. Data was collected with the help of structured questionnaire prepared by literature search. Response of adolescents was recorded through questionnaires. A sensitization workshop was organized as intervention. The same questionnaire was given to them and the effect of intervention was assessed. Statistical analysis of data was done using percentage, proportion and appropriate tests of significance. Result and Conclusions: Only 31.06% adolescents had discussed the topic of reproductive health with some or other person and out of them friends were the major sources (39.2%) of information. Only 38.63% knew the hazards of teenage pregnancy which significantly rose to 89.4% after intervention workshop. The study concludes that the slum adolescents profoundly lack adequate knowledge of sexuality related matters. Even before intervention workshop, unmet need of reproductive health education was 59.1% and 93.93% was the felt need in the post test.