The effects of catecholamines (CA) on various chicken macrophage functions were examined. Macrophage monolayers were exposed to .01, .1, .25, 1, 2, and 5 micrograms/mL of dopamine (DA), norepinephrine (NE) and epinephrine (E) for 1 hr. All CA were toxic for macrophages at 1-5 micrograms dose range resulting in 25-50% cell death. All CA at the .1 and .25 micrograms/mL level increased E. coli and sheep red blood cells (SRBC) phagocytosis by macrophages. The percentage of Fc-receptor positive macrophages increased after CA exposure. Prolonged exposure of macrophages (3 hr) reduced SRBC phagocytosis by DA-treated but not in NE- and E-treated macrophages. However, after 1 hr exposure and 3 hr recovery period, CA-induced changes were reversed in all but DA-treated cultures. Apomorphine and metoclopromide blocked DA whereas propranolol blocked NE and E effects suggesting specificity of the observed effects via catecholaminergic receptors on chicken macrophages. Dopamine and NE (.25 micrograms/mL) did not affect but E exposure enhanced LPS-induced tumoricidal factor production. These findings suggest that CA modulate chicken macrophage effector functions.