Adaptation to stress involves the activity of the hypothalamic-pituitary-adrenal (HPA-) axis. Urocortin 1 (Ucn1) coordinates responses to stressors. An increasing body of evidence suggests that such responses are sexually dimorphic and in females depend on the phase of the estrous cycle. Previously, in the non-preganglionic Edinger-Westphal nucleus (npEW), moderate immunostaining of the estrogen receptor alpha (ERalpha) was demonstrated, whereas estrogen receptor beta (ERbeta) was found to be more abundant. We have aimed at confirming the presence and identifying the type of ER in Ucn1-containing neurons in the npEW in the mouse, and at assessing whether the degree of Ucn1 mRNA expression is gender-related. Using immunocytochemistry, we could not demonstrate ERalpha-immunoreactivity in the npEW, but we did show a high density of ERbeta-immunopositive neurons in the npEW of both male and female mice. A majority of Ucn1-positive neurons showed ERbeta-immunoreactivity in their nuclei. In situ hybridization and RT-PCR did not reveal significant differences in both the number of neurons expressing Ucn1 mRNA and the strength of their Ucn1 mRNA expression. We will extend our gender comparison to other phases of the estrous cycle.