The HIV epidemic has resulted in medical, social and economic consequences. There is general agreement that a safe, effective and affordable preventive HIV vaccine is urgently needed to control the epidemic. To date, over 60 phase I / II trials of about 30 candidate vaccines have been conducted worldwide. In 1991, Thailand was selected by WHO, UNAIDS as one of the countries for potential HIV vaccine evaluation sites, and 10 projects with HIV phase I, II and III trials have been conducted since 1994. Strong national commitment, collaboration both at national and international levels together with infrastructure strengthening and capacity building, are very important for success. The vaccine designs pursued included synthetic peptides, recombinant protein and recombinant viral vectors followed by or with boosting doses of recombinant proteins. All phase I / II trials indicated that the candidate vaccines were safe and produced binding and a certain level of neutralizing antibodies. The recombinant vector vaccines produced both humoral and cell-mediated responses. The AIDSVAX phase III trial conducted in 1999 was the first efficacy trial of HIV vaccine in Thailand that brought valuable information for further HIV vaccine development. Recently, a phase III trial of ALVAC-HIV priming with AIDSVAX® B / E boosting was launched in 2003, and the findings of this trial will be shared with the international community. With committed parties in medical science, government, industry and the community, we hope that we can achieve success in developing a safe and effective HIV vaccine in the near future.