A cross sectional study was conducted amongst students of a school of health technology in Yaba. Lagos. Nigeria to determine their knowledge about HIV/AIDS and their sexual practices. A self-administered questionnaire was used to collect data. Two hundred and thirty-six students out of 250 participated in the study (94% response rate). The mean age was 24.7+5.2 years, 167 (71%) respondents were females while 69 (29%) were males. One hundred and seventy-seven (75%) students were single and 59 (25%) were married. Knowledge on HIV was graded using twenty-nine items on the questionnaire, each scored one mark. A maximum score of 29 was obtainable and respondents with scores greater than 50% were classified as having a satisfactory level of knowledge. Ninety-nine percent had heard about HIV/AIDS through several sources. Knowledge of symptoms, methods of transmission and prevention were generally satisfactory. One hundred and seventy one (72%) students were sexually active, 48% engaged in casual sex and 9% had multiple partners. Of the 171 who were in sexual relationship with a primary partner, 49 (29%) used condoms all the time. One hundred and fourteen (48%) admitted to having casual sex but 60 (53%) used condoms all the time during casual sex. Partner and personal dislike as well as reduction in sexual pleasure were reasons for non-use of condoms. A significantly higher proportion of students in the higher classes (74/94, 79%) possessed a higher level of knowledge than those in the lower class (78/142, 55%, p=0.0003). One hundred and fifty-two (64%) students possessed a satisfactory level of knowledge on the subject, but many engaged in risky behaviour.