Understanding sexual-risk behaviours as defined by a culture presents new challenges for human service professionals. Older African American women constitute the fastest growing group of new cases of HIV in the USA. With heterosexual sex as the primary mode of transmission among this group, there exist minimal programmes that are culture and age-specific in terms of primary and secondary prevention. In an attempt to address this gap in knowledge, this study examined how a group of older African American women defined sexual-risk behaviour. A focus group was conducted with seven women age 45 and older, who were recruited from a community centre. This paper examines the way that sexual-risk behaviour was defined through thematic analysis and conceptualises the locus of sexual risk behaviour as defined by the participants. The major theme of the study was social prescription, how to behave sexually as an ageing adult. Underlying ideas that arose were that unprotected sex occurred out of habit, that impulsivity was associated with risky sex and that older women needed to be aware of warning signs and behaviours of potential mates. Micro- and macro-level implications for human service professionals are discussed.