Young people aged 15-19 in Uganda have a relatively low HIV prevalence rate of under 2%. Nevertheless, people in this group are about to or have just become sexually active and are at high risk of contracting HIV. Young girls are also often targeted by older men, which results in a markedly higher HIV prevalence of girls aged 15-19 compared with boys of the same age. Moreover, the HIV prevalence slightly rose in Uganda in this age group in recent years. Adolescents, therefore, are important targets in HIV prevention programmes. This study aimed at examining the levels of knowledge of and beliefs about HIV/AIDS among adolescents, their sexual behaviour and their attitudes towards people living with HIV/AIDS. It was set in a sub-urban environment in the area of Namasuba in the outskirts of Kampala, the capital of Uganda. Questionnaire data (n=235) was acquired mainly in schools and complementary qualitative data was gathered in five group discussions with 3 or 4 individuals of the same sex (3 male and 2 female groups). The results of this study point out some misconceptions and gaps in knowledge. They also reveal that the stigma attached to HIV-infected people is still considerable. Practical conclusions for HIV/AIDS education and sensitisation programmes are drawn from the data and discussed in this report.