HLA allele frequencies were examined for possible association(s) with the rate of disease progression and with the disease outcome (AIDS diagnosis) in a population of HIV-1-infected individuals. Certain alleles were associated with the relative rate of CD4+ T-cell decline. Association of particular alleles with several disease outcomes associated with infection was also observed. It is important to keep these two aspects (disease progression, AIDS diagnosis) separate when studying HLA in the HIV-1-infected population. Alleles that may play a role in the rate of virus speed by effecting the immune response may be different from those found to be associated with a particular disease. We feel that the only truly informative data, in this regard, can be generated from a relative precise determination of the time of infection (to study disease progression) and adequate numbers of individuals with specific diseases to study specific disease association. If such data can be generated we will have a much better understanding of the pathogenetic process(es) of HIV-1 infection.