Worldwide, there is a consensus that parents must be involved in children's HIV/AIDS education. However, there is little evidence that speaks to this advocacy for improving adolescent health. This study developed and tested four hypotheses about (i) the relationship between parents' and adolescents' knowledge of HIV/AIDS transmission routes and prevention strategies conditional upon (ii) parents' gender, (iii) communication about sexuality, and (iv) the parent–adolescent education gap. The sample consisted of 306 parent–adolescent dyads from the 2002 Cameroon Family and Health Survey. Adolescents were aged 12–19 years. Overall, fifteen items about HIV/AIDS transmission routes and prevention strategies were analysed. Descriptive results showed that parents fared better than adolescents regardless of the AIDS fact considered. An exception was the correct use of condoms (parents 57% vs adolescents 61%). The generation gap probably explains this result: parents are more conservative, reluctant and distant from condoms compared with adolescents, who are more receptive and open to discussing sex with peers. Multivariate ordered logistic regressions showed a significant positive effect of parents' HIV/AIDS knowledge on adolescents' HIV/AIDS knowledge, thus supporting the main hypothesis of direct parental influences. Parent–adolescent communication about sexuality showed positive and significant effects on adolescents' HIV/AIDS knowledge, suggesting an ‘enhancing effect’ when combined with the effect of parents' HIV/AIDS knowledge. Against the background that parents in sub-Saharan Africa do not teach their children about sexuality, the study demonstrated that families can play an important role in HIV/AIDS education. These findings have major implications for HIV/AIDS interventions involving adolescents, parents or both, in fostering accurate HIV/AIDS knowledge among adolescents, which could lead to protective sexual behaviours.