This paper explores how sexual and gender differences in ageing bodies are constructed and negotiated through a discursive analysis of both historical and contemporary literature in sexual medicine and geriatrics. I review several key historical junctures where varying accounts of biological sameness or difference between ageing men and women have been asserted and argue that ageing, in the discourses of biomedicine, presents not only a crisis of gendering bodies but also of heterosexualising them. Through an analysis of clinical research, published practice guidelines, diagnostic indices and their circulation through popular media, I demonstrate how the ‘ageing male’ has been constructed as a biosocial entity, one distinctly different from the ‘menopausal/postmenopausal woman’. I then draw on the sociology of diagnosis to show how cultural narratives of gendered heterosexuality frame a range of related gendered and age-related ‘disorders’ (such as erectile dysfunction and vaginal atrophy), materialising and naturalising social norms and cultural values. As biomedical knowledge and practices realign ideas about sex or gender difference with contemporary technologies and cultural priorities, they do so through largely unchallenged assumptions of heteronormativity. Conclusions suggest how researchers might further explore the ways that biomedical understandings of the ‘life course’ and its unfolding are shaped by hetero-gendered constructions of crisis, risk, optimisation and enhancement.