Vaccines have entered into human clinical trials against infectious diseases and as therapies against cancer. The HIV virus establishes a latent infection at a very early stage and the T cell memory of the infected patient is rapidly destroyed. However, results of immunotherapy after DNA and protein immunization show that vaccine-induced immune responses might be present for a long period of time. Patients subjected to therapeutic immunization appear to do well, and to have a small immunological advantage, which, however, will have to be improved. The vaccine therapy should start early, while adequate reservoirs of appropriate T helper cells are available and still inducible. The DNA vaccines induce a relatively long-lived immunological memory, and gene-based immunization is effective in inducing cytotoxic CD8(+) T cells and CD4+ helper cells. Protein vaccines, on the other hand, primarily give T cell help. It thus appears that DNA and protein approaches to HIV immunization complement each other. A surprisingly broad reactivity to peptides from different subtypes of HIV was identified in individuals infected with several subtypes of HIV.