To identify factors that are associated with condom use to aid in the understanding of how to change the behavior of those young people who have sex without using condoms.The article reports data from 932 sexually active grade 10-12 students from a sample of 72 public secondary schools in seven Australian states and territories. The data were collected using a cross-sectional, self-report questionnaire.Boys were more likely than girls to report that a condom was used the last time they had sex. For boys and girls, communication with a partner about avoiding infection with HIV/STDs, the belief that more peers use condoms, and a higher perceived risk of becoming infected with HIV/STDs were associated with using a condom, as was lower knowledge of STDs. The use of oral contraception and the unavailability of condoms were reported by the students as prominent reasons for non-use of condoms. Number of sexual partners in the past year and type of relationship with partner on the most recent occasion were not associated with condom use.Adolescents are more concerned with unwanted pregnancy than with disease prevention. School students more at risk are not more likely to take the necessary precautions to protect themselves from HIV/STDs.