Objective: To examine HIV/AIDS knowledge, perceptions of knowledge and sources of HIV information among university students in four countries with different HIV prevalence rates. Methods: A survey was completed by 2,570 randomly selected university students from the USA, Turkey, South Africa and Nigeria. Logistic regression analysis was used to identify the association between accurate HIV/AIDS knowledge, demographic characteristics and frequency of exposure to information sources. Results: Compared to US students, the HIV/AIDS knowledge of Turkish students was more likely to be inaccurate and the knowledge of South African and Nigerian students was more likely to be accurate. South African students were the most exposed to HIV/AIDS information and Turkish students were the least exposed (p?<0.001). Men were more likely to demonstrate accurate HIV knowledge than women. A higher percentage of students from South Africa and Nigeria (countries with high HIV prevalence) incorrectly perceived themselves as being very knowledgeable about HIV/AIDS. Marital status, year of university education and type of study (part time or full time) were associated with level of knowledge. Frequency of exposure to HIV/AIDS information was not associated with knowledge. Conclusion: More students in countries with higher HIV prevalence had accurate HIV/AIDS knowledge and poorer perception of their level of knowledge than students in countries with low prevalence. Governments in the countries studied should ensure that young people receive accurate HIV/AIDS information, with special attention paid to educating young women.