Twenty-five years of experience with the human immunodeficiency virus (HIV) have established that it is relatively difficult to transmit. The chance of medical personnel acquiring this virus by needlestick injury is only 0.3%. Similarly, the odds of an HIV-positive male infecting a female partner during one unprotected sexual encounter is 9 in 10,000. Furthermore, the per-act risk of infection from penal-anal intercourse with an HIV-positive male partner is established at 82 in 10,000. Since those who are not infected by such exposures do not develop antibodies against HIV, there must be an earlier line of defense. The global diffusion pattern of HIV/AIDS is strongly suggestive of a protective role for the trace element selenium. It is hypothesized here that the body's antioxidant defense system, especially the selenoenzyme glutathione peroxidase, acts as an initial defense against viral infection, preceding the formation of antibodies. For this reason, HIV is having its greatest difficulty in infecting those with diets elevated in amino acids and the trace element selenium which, when eaten together, stimulate the body's production of glutathione peroxidase.