Gonadotropin−inhibitory hormone (GnIH) acts to inhibit reproduction at all levels of the hypothalamo−pituitary−gonad (HPG) axis¹ . GnIH in the hypothalamus increases with acute stress in some birds and mammals^2,3 , thus representing a mechanism by which stress can inhibit reproduction. Zebra finches are opportunistic breeders for which timing of breeding is closely associated with unpredictable environmental cues. Thus, the zebra finch GnIH system may be more sensitive to stress than that of seasonal and/or continuous breeders. To test this, we collected tissues from males and females in mixed−sex aviaries immediately after capture or following 60 min of restraint. As expected, restraint significantly increased plasma corticosterone in males and females. Contrary to studies on other species, immunocytochemistry for GnIH revealed significantly fewer GnIH immunoreactive (−ir) cell bodies in the stressed birds. There was no sex difference in GnIH cell number in either treatment or control animals. Quantitative PCR of pituitary tissue revealed a significant decrease in FSH-b expression (p<.04) in stressed females only, suggesting that the reduction in GnIH immunoreactivity seen in stressed birds may be due to GnIH release rather than a reduction in synthesis as seen in other species. Quantitative PCR of gonadal tissue showed a significant increase in GnIH expression in testes of stressed animals but no significant change in ovarian tissue. Our data suggest that although GnIH responsiveness to stress appears to be conserved across tested species, the specific tissue response and level of GnIH regulation is not. Variation in the GnIH response to stress among species might be the result of ecological adaptations or species differences in GnIH function.