Inter-generational sex is an important driver of the AIDS epidemic in Southern Africa, contributing to the high incidence of HIV among young women. We conducted 12 focus group discussions with women aged 15-24 years and 11 with men aged 40-55 years in urban and rural locations in Botswana, Namibia and Swaziland. There was consensus that inter-generational sex is commonplace. The young women were clear they had sex with older men to get money and material goods. In urban sites, they spoke about requirements for a "modern" lifestyle and to keep up with their friends, but in rural sites they also said they needed money for school fees, food and household goods. Young women used disparaging names for the older men and they were well aware of the risk of HIV from inter-generational sex. They believed older men were more risky than younger men: They were more likely to be infected and it was harder to negotiate use of a condom with them. They were willing to take the risk to get what they wanted; some also had a fatalistic attitude. Older men described sexual motivation and blamed young women for seducing them. They believed there was a higher risk of HIV from younger women, because they have more partners and do not insist on using a condom. But this did not deter them from taking the risk. Older men and young women discount the risks of inter-generational sex against short-term benefits. Isolated efforts to increase risk awareness are unlikely to be effective. Making older men aware they are ridiculed by young women may be a promising approach, combined with interventions that give alternatives to young women and increase their self-worth.