Many years after the outbreak of HIV/AIDS, public health exertions have not been able to limit the spread of the diseases. This study, therefore, seeks to widen the scope of investigation in regard to the socio-demographic factors that determine risky sexual behaviours among all persons aged 15-59 years old. The present study used the 2016 South African Health and Demographic Survey data to examine the social and demographic determinants of risky sexual behaviours among people of reproductive ages (15-59), using the binary logistic regression model. The results showed that socio-demographic variables, namely; age, race, level of education, wealth index and relationship status, generally predict sexual risk-taking behaviours among South African men and women. Young people aged 20-24years; the Black Africans as well as never married people are overrepresented among those involved in unsafe sexual practices. However, those who are ever married or cohabiting are less at risk of engaging in risky sexual behaviour whereas education provides a degree of protection, more so for females than males. The findings from the study support actions to improve sex education for all individuals that are vulnerable.