Ducks given corticotrophin (ACTH) i.m. for 5 days secreted significantly more nasal fluid in response to an i.v. injection of 0·5 m-NaCl. However, blood glucose and plasma potassium concentrations also increased in the birds given ACTH and when these changes in blood composition were produced by injecting glucose or KC1, an effect similar to that of ACTH was obtained, suggesting that glucocorticoids influence the salt gland indirectly rather than, or as well as, directly. The concentrations of Na+ and K+ in the nasal fluid were decreased by ACTH, an effect not mimicked by glucose or KC1, and this might suggest some direct influence on water movements in the salt gland. ACTH increased nasal secretion in response to a minimal stimulatory salt load approximately 15 min after i.v. injection and this increase coincided with a marked rise in blood glucose concentration.