a b s t r a c tThis study assessed sexual orientation and psychobiological stress indices in relation to salivary sex hormones as part of a well-validated laboratory-based stress paradigm. Participants included 87 healthy adults that were on average 25 years old who self-identified as lesbian/bisexual women (n = 20), heterosexual women (n = 21), gay/bisexual men (n = 26), and heterosexual men (n = 20). Two saliva samples were collected fifteen minutes before and fifteen minutes after exposure to a modified Trier Social Stress Test to determine testosterone, estradiol, and progesterone concentrations via enzyme-immune assaying. Mean sex hormones were further tested in association to stress indices related to cortisol systemic output (area under the curve with respect to ground) based on ten measures throughout the two-hour visit, allostatic load indexed using 21 biomarkers, and perceived stress assessed using a well-validated questionnaire. Results revealed that lesbian/bisexual women had higher overall testosterone and progesterone concentrations than heterosexual women, while no differences were found among gay/bisexual men in comparison to heterosexual men. Lesbian/bisexual women and heterosexual men showed positive associations between mean estradiol concentrations and allostatic load, while gay/bisexual men and heterosexual women showed positive associations between mean testosterone and cortisol systemic output. In summary, sex hormone variations appear to vary according to sexual orientation among women, but also as a function of cortisol systemic output, allostatic load, and perceived stress for both sexes. (R.-P. Juster). explanations of non-heterosexual behavior have often hypothesized a dysregulation of sex-specific hormone profiles, resulting in anomalies in the organizational and activational effects of these hormones on the neurodevelopment of circuitry underlying species-specific sexual behavior. Animal models involving prenatal androgen deficits, for example, were first believed to cause male homosexuality (Phoenix et al., 1959), while prenatal androgen overabundance presumably resulted in female homosexuality. Our study endeavours to show that such sex hormone differences assumed to be attributable to sexual orientation are also modulated by unexplored stress phenomena.Advances in behavioral neuroscience has led to the introduction of sophisticated genetic models involving non-functional androgen receptors, further allowing researchers to characterize the relation-Konstanzer Online-Publikations-System (KOPS) URL: http://nbn-resolving. de/urn:nbn:de:bsz:352-2-1f6t7wu8qvgcl6 Erschienen in: Psychoneuroendocrinology ; 72 (2016). -S. 119-130 https://dx.