In the continued, and likely to be prolonged, absence of an effective vaccine, the scientific community needs to find an alternative way to prevent the sexual transmission of human immunodeficiency virus type 1 (HIV-1). The global HIV-1 epidemic is fuelled by heterosexual transmission, which is how about 80% of the 40 million people now infected acquired this lethal virus.1 Most (∼95%) new infections now occur in the developing world, almost half among women.1 Although HIV-1 infection is not particularly easy to acquire sexually, the lengthy duration of asymptomatic infection, the high frequency with which at least some people have sexual intercourse, and various exacerbating circumstances, all conspire to render HIV-1 readily transmissible in the long run. What can be done about this? Education and condom distribution play important roles in reducing transmission, but sexual behaviour is notoriously difficult to modify, particularly among young people, and there are often cultural obstacles to overcome when persuading men to use condoms routinely, if ever. A pharmaceutical intervention would be invaluable. A transmission-preventing compound that women could apply, covertly if necessary, to the vagina or rectum prior to intercourse could save millions of new infections, and thence lives, each year. Sounds simple? Sadly, it is not. And the research community, particularly the pharmaceutical industry, has not rallied to the cause. Is this because the problem does not involve particularly sexy science? Or because no easy profit is perceived to come from making and marketing a topical microbicide?