To establish the optimal dose and sampling times for the ACTH stimulation test in racing pigeons, plasma corticosterone concentrations were measured in experimental animals at 0, 30, 60, 90, 120 and 150 min after intramuscular administration of different doses of ACTH(1-24). Baseline corticosterone concentrations varied between less than 0.2 and 1.24 microg/dl. To evaluate adrenocortical function the clinician is advised to take a blood sample before and at 60 or 90 min after stimulation with 50 microg ACTH or at 30, 60, 90 or 120 min after stimulation with 125 mug ACTH. In healthy individuals a ten- to hundred-fold increase over baseline (t=0) corticosterone concentrations and absolute concentrations in the range of 2.2 to 15.0 microg/dl can be expected in the post stimulation sample.