We propose to test, by DNA linkage analysis of family pedigree members, the following interrelated hypotheses: 1) that sexual orientation is genetically influenced; 2) that the development of Kaposi's sarcoma and other outcomes of HIV infection in male homosexuals is affected by host susceptibility genes, circulating sex hormone levels, or HLA haplotype; and 3) that alcoholism and other psychobehavioral conditions are associated with homosexuality on a genetic basis and/or influenced by candidate behavioral loci. The subjects for these studies will be self-identified male and female homosexual probands and their relatives from families in which there are at least two individuals with homosexual orientation. All subjects will be adults, and will be referred through NIH physicians, private practitioners, and gay and lesbian organizations. Subjects will undergo a sexual orientation and behaviors interview, a psychiatric interview, and phlebotomy for HIV testing, HLA determination, endocrine measurements, and preparation of DNA from cultured lymphocytes. The DNA samples will be analyzed for a series of genetic markers that span the human genome and for candidate loci chosen for function.