OBJECTIVE: This study aimed to determine the knowledge and attitude of adolescents towards sexually transmitted disease (STD), urinary tract infection (UTI), and HIV in a rural area of Pelaihari, South Kalimantan and its association with previous education given. METHODS: An observational study was conducted in five high schools in Pelaihari, South Kalimantan. The population was randomly selected and interviewed based on validated questionnaire. RESULTS: From 256 subjects included in this study, 138 subjects were boys (53.9%). The median age of subjects was 16 years old (14 – 18).  Most of the subject (74.6%) still assumed that STD cannot be cured and most of them (66.8%) also agreed to minimize contact from people with STD. More than half of the boys and girls (59.4% and 70.3%) still did not know the sign and symptoms for UTI. Most of the boys were circumcised (88.4%) and almost all of the girls (96.6%) had well attitude regarding hygiene in the genital area. More than half of the subjects (74.6%) still thought that HIV cannot be controlled using antiretroviral drugs and almost all of them (84.8%) agreed that they need more information about HIV. Previous education was found to be effective to improve knowledge about HIV (p < 0.001) but found ineffective (p > 0.05) in STD and UTI topics.                                                                                                                                              CONCLUSION: Knowledge and attitude towards STD, UTI, and HIV among adolescents in Pelaihari, South Kalimantan still need to be improved. Previous education was found to be effective in certain subject. Future research regarding methods of education appropriate for adolescent in a rural area is still needed.