ABSTRACT
The
anterior hypothalamus of the brain participates in the regidation of male-typical
sexual behavior. The volumes of four cell groups in this region (interstetial nudei of the
anterior hypothalamus, INAH 1, 2, 3, and 4) were preswned in postmortem tissite from three subject groups: women, men who
were presumed to be heterosexual,
and homosexual men. No differences were found between the groups in the volumes of INAH 1, 2, sau 4. As has been
previouslv, INAH 3 was more than
twice as large in the heterosexual men as m the women. It was also, however,
more than twice as large in the heterosexual men as in the homosexual men. This
finding indicates that INAH is dimorphic with sexual orientation, at least in
men, and suggests that sexual orientation has a biological substrate.
