The effect of triamcinolone acetonide (0.09 mg/kg of body weight, IM) on serum osteocalcin concentration was studied. Two groups of horses were investigated and included clinically normal horses (group 1, n = 5) and horses with chronic obstructive pulmonary disease (group 2, n = 5). Before treatment, results of a t-test did not reveal any significant difference in serum osteocalcin concentration between the 2 groups. After treatment, a significant (P < 0.05) decrease in serum osteocalcin concentration was observed for both groups. Osteocalcin concentration in individual horses reached a minimum by 24 to 48 hours after treatment. In both groups of horses, serum osteocalcin response to glucocorticoid administration was similar. In 7 of 10 horses, return to pretreatment values was observed after 28 days. Pretreatment values for the other 3 horses were reached between 62 and 150 days.