This cross-sectional study conducted in 2007 in South Delhi, India aimed to assess adolescent school girls' knowledge, attitudes and perceptionsátowards STIs/HIV and safer sex practices and sex education and to explore current sexual behavior. Two hundred and fifty-one female students from two senior secondary schools completed self-administered questionnaires. Over 33% of students did nto have accurate knowledge of the symptoms of STIs other than HIV. Thirty percent thought HIV/AIDS was curable; 49% though condoms should not be available to youth; and 41% were unclear whether the contraceptive pill protected against HIV, but 32% thought it should only be prescribed to married women. Gender-based sex education covering STIs, safer sex strategies and contraception is vital in India.