The effects of fighting and footshock on circulating adrenocorticotropin-like immunoreactivity (ACTH-LI), cortisol, corticosterone, beta-endorphin-like immunoreactivity (beta-EP-LI), and beta-lipotropin-like immunoreactivity (beta-LPH-LI) were examined. In the first experiment, catheterized males were paired with large, ovariectomized females for 15 min. Submissive males exhibited significant increases in plasma ACTH-LI, cortisol, corticosterone, and beta-EP-LI. In the second experiment, two males were paired to determine whether the hormonal response in submissive animals was different from that in dominant hamsters. The pattern and magnitude of the hormonal response was also compared to that following a commonly used stressor-footshock. Footshock was associated with large increases in each of the plasma hormones measured. Submission, but not dominance, was associated with smaller, but still significant, increases in ACTH-LI, cortisol, beta-EP-LI and beta-LPH-LI. The data indicate that fighting is not a generalized stressor. "Losing," in particular, appears to be an example of a biologically relevant stressor.