Human immunodeficiency virus (HIV) has one of the highest incidence and mortality rates of any infectious disease, with more than 33 million people infected worldwide. Specifically, HIV causes the destruction of helper T cells, ultimately resulting in the suppression of the immune system and leaving its human host susceptible to countless other pathogenic agents. The development of an effective HIV vaccine has continued for more than 20 years. But the use of preventative vaccines using traditional vaccine technologies, which have proven successful for other diseases, has thus far failed with HIV. One vaccine, AIDSVAX, was the first HIV vaccine to reach a phase III efficacy trial, but has not yet been shown to eradicate HIV. Hope now lies in the development of therapeutic vaccines using novel technologies. One such vaccine is ALVAC-HIV, which, when used in conjunction with other vaccines (AIDSVAX or Lipo-6T with IL-2 injections) has shown a great deal of promise in clinical trials suppressing viral replication and improving the immune system. Other therapeutic vaccines, such as Ad5, however, have been unsuccessful. While many believe developing an effective HIV vaccine to be impossible, efforts continue into researching its structure, transmission, immune system suppression, genetic variability, and immune system evasion. As long as research continues, hope remains that someday an effective vaccine will be developed.