The majority of donor blood in Zimbabwe comes from school-based donors. Zimbabwe has one of the highest HIV prevalences in the world and the age at which the infection is acquired is decreasing. This is a serious threat to the safety of blood supply. The prevalence of HIV has been low among the youth the majority of whom are still going to school and between the ages of sixteen and nineteen years. However, due to the changing socio-economic environment, sexual behavioural patterns have also changed. It is now necessary to evaluate these changes in order to guarantee safe blood transfusion. To determine the prevalence of HIV among adolescent donors during the period between 2002 and 2003. Cross-sectional retrospective study, National Blood Transfusion Service (NBTS). All school based donors and others between 16 and 19 years of age. The number of donors who were HIV positive in this age group. Data on donors was collected from computer files at the National Blood Transfusion Service (NBTS) Information Technology (IT) department. Prevalence of HIV was determined and categorised according to gender, age and the type of school the donor attended. The prevalence of HIV in 2002 and 2003 were 0.48% and 0.38%, respectively. Sixty-six per cent (66%) of HIV positive donors had donated for the first time. The prevalence in both periods was much higher in female donors than male donors. In 2002 males and females had prevalence of 0.28% and 0.66%, respectively. In 2003 males and females had prevalence of 0.18% and 0.55%, respectively. The overall highest prevalence (0.90%) was found between the 16-19 year age group who were not going to school (others). In 2002 female day schools had the highest (0.87%). The lowest prevalence (0%) was found in male boarding schools. In 2003 the highest prevalence (1.61%) was found in the 16-19 year age group who were not going to school (others). The lowest prevalence (0) in the same year was found in male boarding scholars. It can be concluded that the majority of HIV positive school based donors are first time donors. Female scholars and those of the same age group who are not going to school have the highest risk of donating HIV positive blood than male donors. The prevalence of HIV in adolescent blood donors decreased with age. It is recommended that active donor recruitment should be in favour of the low prevalence groups.