Characteristics of learners who become peer educators are rarely explored despite the potential relevance to the success of peer education programmes. Fifteen high schools selected to implement peer education HIV prevention programmes in South Africa were recruited. A total of 2339 Grade 10 learners were surveyed and comparisons were made between socio-demographic characteristics, key skills, school experience and sexual behaviour of those students who had volunteered or been chosen by teachers to be peer educators (n = 295) and their fellow students (n = 2044), the potential recipients of the programme. On most of the socio-demographic variables, school experiences, aspirations, sexual debut and use of condoms at last sex or whether they had been tested for HIV status, there were no significant differences between the two groups. Volunteers and teacher-chosen peer educators tended to be younger than their classmates (16.19 versus 16.52, P less than 0.0001), score higher on a goal-orientation scale (3.27 versus 3.15, P =less than 0.0001) and had more access to basic resources [electricity (97.9% versus 94.0%, P = 0.006), a bicycle (41.9% versus 32.7%, P = 0.004) or car (50.2% versus 41.0%, P = 0.005)]. Further research is needed to explore specific peer educator characteristics and recruitment and selection approaches that are associated with effective HIV prevention interventions.