This work examines sexual behavioural change and the likely predisposing factors in the era of HIV/AIDS among young adults in Uganda and South Africa. It explores the potential role of young adults' self-perceived risk of HIV infection in sexual behavioural decisions regarding adoption of safe sex practices, in particular 'use of condoms' and 'limiting number of sexual partners '. This work further recognises that Uganda and South Africa are countries with social, cultural, economic, and political contexts, which contexts have been described by many as inextricably linked with sexual behaviour, and which often determine the choices young adults make regarding sexual activity. These are therefore examined. In order to achieve this, a rigorous examination and analysis of self-perceived risk of HIV/AIDS in relation to societal factors was done to determine which variables of the two categories best explains sexual behaviour. This is placed in the context of young female adults between the ages of 15 to 24 in Uganda and South Africa. The formulation of this study, which places emphasis on examining the potential role of self-perceived risk of HIV/AIDS as a predisposing factor for sexual behavioural change, and in Uganda and South Africa is based on a number of aspects as highlighted below: • That both Uganda and South Africa at one point or another were and/or are faced with high prevalence levels of HIV/AIDS; • That both have and/or are yet to be faced with high mortality, which is HIV/AIDS related and such profound consequences will/or have had inadvertent effects on individual, both socially and economically. In some respects, this has also affected individual perceptions regarding HIV infection; • Recognition that the progression of HIV/AIDS in Uganda was much faster than in South Africa, and this meant higher prevalence, higher mortality rates, which then triggered both government and non-governmental response towards preventing further spread. Since these factors are beginning to emerge in South Africa, one therefore asks the question as to whether the pandemic will take similar trends as those reported in Uganda. This would also enable the identification of similarities and differences in the likely determinants of sexual behavior considering these countries have different backgrounds; • In both countries, education programmes have been rigorous and that the level of awareness is at a point that would enable sexual behavioural change to occur; • A recognition that in Uganda, as shown in a number of reports and existing literature, the prevalence of HIV has declined and for this reason, it has become imperative to try and examine the likely factors leading to reduced HIV/AIDS prevalence, and to compare with what is happening in South Africa. This would enable the examination of any possible lessons that could be learnt in the reduction of the prevalence in South Africa. In the quest to achieve the set goals, a number of steps were undertaken which included looking at available literature and more importantly analysing two sets of Demographic Health Survey (DHS) data. The South Africa Demographic Health Survey of 1998 (SADHS) and the Ugandan Demographic Health Survey (UDHS) of 2000/1. All young female adults between the ages of 15 to 24 were selected from both data sets. 3,229 and 4,559 young female adults were selected in Uganda and South Africa respectively leading to a total sample size of 7,688. Findings showed that self-perceived risk of HIV/AIDS was one of the factors that did impact on sexual behaviour. This was more prominent in Uganda and less so in South Africa. Other factors found to affect sexual behaviour included age of respondent, socio-cultural and to a small extent, socio-economic factors. The conclusion that can be drawn from this work shows clearly that self-perceived risk of HIV/AIDS is an important factor determining sexual behaviour, but also shows that some societal variables are important. Therefore, in the face of HIV/AIDS and with increased levels of number of people experiencing deaths due to AIDS, selfperceived risk of HIV/AIDS is a factor worth considering when looking at sexual behaviour. As part of the recommendations, education programmes yet to be formulated should take into account the effect of HIV and AIDS on sexual behavioural change