This book has highlighted the problem of non-tobacco substance use and sexual abuses along with HIV/STIs, among ''Hard-to- Reach Population'' like street children. The reported prevalence of non-tobacco substance use was 30%; 9% reported having been sexually abused. Certain risk factors (age, lack of contact with family, orphan children, night stay at public place etc.) were documented to be associated with substance use and sexual abuses. One percent HIV sero-prevalence in street children is a matter of concern and need immediate intervention to check a potential epidemic in India. Without any intervention; it will definitely spiral and pose a serious health hazard which country may not deal with. This book will definitely be informative for all the social scientists and public health specialists working in the field of HIV/AIDS research.