Subjects are healthy adult volunteers either at high risk for HIV infection or already known to be seropositive, who will donate blood for in vitro tests of T-cell function and in vitro responses to synthetic peptides corresponding to sequences from HIV proteins.

Subjects are healthy adult volunteers either at high risk for HIV infection or already known to be seropositive, who will donate blood for in vitro tests of T-cell function and in vitro responses to synthetic peptides corresponding to sequences from HIV proteins.

Inclusion criteria for the at risk group will be a statement from the donor that he is an active homosexual or bisexual.

Homosexual donors must not have AIDS.