Synopsis Knowledge of sex and human reproduction among the youth has been receiving greater attention in developed countries. But in a developing country like India, the research studies are very meager. So far very little work has been undertaken to know the knowledge of sex and human reproduction among unmarried and backward class youth. The present study mainly focuses on the levels of awareness of sex and reproduction among rural unmarried girls belonging to the three different communities viz., the Harijans, the Muslims and the caste Hindus. The study is confined to Chittoor District in the State of Andhra Pradesh based on a sample size comprising 600unmarried girls in the age group of 17 to 19 years. This is a unique attempt to understand the concept formation among unmarried rural adolescent girls.