A quarter of a century of AIDS responses has created a huge body of knowledge about HIV transmission and how to prevent it, yet every day, around the world, nearly 7000 people become infected with the virus. Although HIV prevention is complex, it ought not to be mystifying. Local and national achievements in curbing the epidemic have been myriad, and have created a body of evidence about what works, but these successful approaches have not yet been fully applied. Essential programmes and services have not had sufficient coverage; they have often lacked the funding to be applied with sufficient quality and intensity. Action and funding have not necessarily been directed to where the epidemic is or to what drives it. Few programmes address vulnerability to HIV and structural determinants of the epidemic. A prevention constituency has not been adequately mobilised to stimulate the demand for HIV prevention. Confident and unified leadership has not emerged to assert what is needed in HIV prevention and how to overcome the political, sociocultural, and logistic barriers in getting there. We discuss the combination of solutions which are needed to intensify HIV prevention, using the existing body of evidence and the lessons from our successes and failures in HIV prevention.