In the last seven to eight years, Antiretroviral Treatment (ART) has received an increasing amount of attention internationally. It has come to be viewed as an important way of preventing new HIV infections and prolonging HIV-positive peoples' lives. In late 2003 the increased attention, amongst other factors, led the South African government to publish a comprehensive health care plan stating that all citizens in South Africa who need ART should receive it by year 2009. Patients' adherence and their sexual behavior are crucial to the success of ART. This thesis focuses on what factors influence patients' sexual behavior after commencing ART. It will especially look at ART patients' perception of their own infectiousness, as studies have suggested that lower viral loads caused by ART will increase their sexual risk behaviour. The research was conducted on patients attending Ithembalabantu Clinic in KwaZulu-Natal, South Africa. Qualitative and quantitative data were used in the study. The quantitative data involved 271 face-to-face interviews based on a survey. The qualitative data involved conducting 20 semistructured interviews. The results indicated that consistent condom use was high among the sample population (72%), and only two females and seven males having multiple partners (7%). However, due to ART just recently having been introduced in South Africa, the average time spent on ART was 14 months. The findings reveal that a partner's attitude to HIV/AIDS and the levels of communication and openness in a relationship influenced consistent use of condoms. The use of condoms was significantly related to knowledge of partners' status. A high level of sexual assertiveness amongst the females in the sample might have made it easier for them to negotiate condom use. The stage at which members of the sample population entered the relationship was also a predictor of condom use. People who were unemployed and over 35 years in age were less likely to use condoms consistently.