The aim of this research was to describe the sexual behaviour and HIV/AIDS risk perception in two cohorts of Spanish university students. A cross-sectional design of two cohorts was employed. A total of 230 university students in 2004 (Mage=19.77; SD=1.73; 72.6% females) and 264 in 2012 (Mage=19.47; SD=1.73; 73.5% females) were recruited. A self-developed questionnaire on sexual behaviour was administered. A MANOVA per cohort, gender and age was performed. The results revealed that there were no differences between the cohorts regarding sexual practices. About one-fifth of sexually active young people used condoms regularly but not always, around one-sixth sometimes or never used them, half of the respondents did not usually require their sexual partners to take an HIV test and only the ten percent had ever undergone it. Three quarters of the subjects perceived some degree of invulnerability to HIV/AIDS. Spanish females perceived themselves more invulnerable.