Despite structural and functional conservation across vertebrate species, the glucocorticoid receptor has been minimally studied in comparison to other biological targets for endocrine-disrupting compounds in aquatic systems. Because prolonged use of pharmaceutical glucocorticoids in humans has been linked to osteoporosis and impaired bone growth, we hypothesized that the ability of teleost fish to regenerate fins following damage may be inhibited by exposure to synthetic glucocorticoids in the environment. In the present study, we examined fin regeneration following a 7 days waterborne exposure of juvenile fathead minnows (