The following research was made to determine the relationship between “the standard of knowledge and preventive practices about sexually transmitted infections HIV / AIDSin students from Juan Miguel Perez Rengifo high school, June – August 2012. The design of the research is correlational descriptive of transverse section. The sample, no probabilistic for our own interest, was seventy seven (77) students of the 5th grade from Juan Miguel Perez Rengifo high school who achieved with all our criteria of inclusion. We used the quantitative method by using questionnaire of twenty (20) questions with three (3) answers and those questions measured the knowledge in dimension of concepts, kind of STI, how to prevent, how to transmit, transmitter agents, how to care and how to diagnose; and a questionnaire of eighteen (18) questions with descriptive scale, in the dimensions of preventive pract...