The epidemic of HIV-1 continues to spread throughout the world despite current prevention efforts. Between 1993 and 2000 the World Health Organization projects that at least 26 million people will become infected with HIV-1 – an average of 10,000 people a day over the 7-year period. While a substantial increase in the financial and human resources available for prevention activities would reduce the number of new infections, there is a growing realization that the current range of prevention activities will not be able to halt the epidemic. Other measures are urgently required. The development of safe and effective preventive HIV-1 vaccines would dramatically improve the prospects for controlling the HIV epidemic provided they be made accessible to those at greatest risk of infection. Meeting participants acknowledged the unprecedented effort that has been made by the scientific community to understand the biology and pathogenesis of HIV since its discovery as the etiologic agent of AIDS in 1984. In addition, there has been considerable interest shown by national and international public and private sector institutions in the development of HIV vaccines. These ongoing efforts, while constrained by budgetary and human resource limitations, have lead to major advances in scientific knowledge, and there are now encouraging signs that the development of a preventive HIV vaccine may be possible. A number of obstacles, however, hinder product development, and make it unlikely that a vaccine appropriate for use throughout the world will be developed and made available in a timely fashion unless remedial actions are taken. In 1993 over US$ 1.5 billion was spent worldwide on HIV prevention and over US$ 5 billion on HIV-related health care. Yet, in the same year less than US$ 160 million was invested worldwide by the public and private sectors in HIV vaccine research and development. This was considered insufficient given the current and rising health, humanitarian, social, and economic costs of the HIV epidemic. The investment of additional resources was viewed as potentially making a significant difference, especially if targeted at the critical gaps in current development efforts. The national research agencies of the developed countries have been playing a key role in vaccine research. Product development activities, however, have been left almost exclusively to the pharmaceutical and biotechnology companies. In the current environment the incentives for industry to invest substantially in the development of a preventive HIV vaccine are limited – there are a number of other products with more attractive investment prospects. To overcome this market failure and ensure more active industry participation, positive steps will need to be taken. The dominance of the national research agencies of the developed countries and the pharmaceutical and biotechnology companies in HIV vaccine research and development has meant that current efforts are directed almost exclusively towards vaccine products catering to the needs of the developed world. This emphasis raises cause for concern about the ultimate provision of an HIV vaccine to those in greatest need – over 90% of new infections are occurring in the developing world. For example, the industry investment in product development has, in general, been targeted at those vaccine approaches that are perceived as the safest, and has been based upon the sub-types of HIV-1 found in developed countries. Approaches that have technical characteristics that may make them better suited for use in developing countries are not being pursued aggressively. The rationale is that proving efficacy of a vaccine is the priority, following which other products will be developed in a sequential fashion. Given the many scientific uncertainties remaining, participants at the Bellagio meeting concluded that the development and testing of multiple empirical approaches in a parallel fashion, rather than sequentially, will be a faster route to the development of safe, effective, and inexpensive vaccines appropriate for widespread use. The primary focus of current efforts on the sub-types of HIV-1 found in developed countries may also delay the evaluation of candidate vaccines by restricting the sites where clinical trials can be performed. The unique nature of the HIV epidemic and its devastating potential consequences led the participants at the Bellagio meeting to conclude that a new global initiative with the primary mandate of accelerating the development of preventive HIV vaccines appropriate for worldwide use should be established. A new global HIV vaccine initiative was viewed as the most effective method to accelerate the development of safe and effective preventive HIV vaccines in the shortest time possible. The initiative should focus on reducing the obstacles to vaccine development and filling the gaps in the current effort. By focusing on the obstacles and gaps, the initiative was seen as complementing, not competing with, existing national and international activities. Success in developing an HIV vaccine will require the involvement of both the public and private sectors. Collaborative ventures between the private and public sectors have been fruitful in a number of other sectors in galvanizing product research and development, while still respecting corporate profit motives and independence. A range of potential models and sources of funding for the new initiative was suggested. A small funding secretariat, or task force, with an international scientific steering committee was viewed as the most appropriate structure.