The purpose of the study was to identify factors associated with the HIV transmission rate in 18 to 24 month-old children enrolled in the PMTCT programme at two selected City of Tshwane clinics. Mother-to-child transmission of HIV during labour and breastfeeding accounts for 40% of all HIV infection in children. The prevention of mother-to-child transmission of HIV programme is one effective strategy to reduce the rate of HIV infection in children. The HIV transmission rate was low at six weeks of age but increases at 18 to 24 months of age due to several factors. The researcher selected a descriptive retrospective correlational research design. A structured questionnaire was used to collect data from 60 mothers of children aged 18 to 24 months on the PMTCT programme and a data-collection form to collect data from 152 clinic records of children of the same age on the programme. The study found that the PMTCT guidelines were not properly adhered to by the nurses and the respondents. Prophylactic treatment was not provided as required and mixed feeding was prominent. The uptake of HIV test at 18 to 24 months was low compared to at 6 weeks. The transmission rate was high at 18 to 24 months compared to at 6 weeks. No factors were associated with the transmission rate / Health Studies / M.A. (Public Health)