From 1988 to 1994, first-year students in a large introductory class at Macquarie University completed a questionnaire regarding sexual practice, knowledge of transmission of human immunodeficiency virus (HIV) and understandings of safe sex. Data from 18- and 19-year-old students were analysed to examine changes over time among recent school leavers. Approximately 58 per cent were sexually experienced, young men were more experienced than young women, and both had more experience with regular than with casual partners. The number of partners did not vary over the years, most respondents having had one or two partners. Changes over time were found with respect to condom use, particularly with regular partners. The percentage using condoms "always' with casual partners was greater, having increased to around 60 per cent. Accuracy of knowledge relating to safety of sexual practices with casual and with regular partners increased over time, particularly with respect to regular partners. While both accuracy of knowledge and safety of practice increased with time, there was no relationship between these two variables in any one year. The findings suggest that there has been normative change with regard to condom use and that this has occurred within a reasonably static and unchanging set of sexual practices. Sex education appears to be one of the factors contributing to this change.