Serial physiological responses were examined for 150 min from captive collared peccaries during immobilization with ketamine hydrochloride. Rectal temperatures decreased significantly (P < 0.01) during anesthesia. Serum concentrations of total proteins, albumin, cholesterol, alanine aminotransferase, and calcium declined significantly (P < 0.05) during the first 45 min post-immobilization before stabilizing. Concentrations of lactate dehydrogenase and alkaline phosphatase in sera showed similar but nonsignificant (P > 0.05) trends. Inorganic phosphorus and aspartate aminotransferase concentrations increased significantly (P < 0.05) throughout the trial. Concentrations of serum glucose and glucocorticoid during the immobilization period were highly variable between individuals. Serum electrolytes, urea nitrogen, creatinine, gammaglutamyl transferase and progesterone were not significantly (P > 0.05) affected by immobilization. Elevations in serum testosterone were noted. Results indicated appropriate sampling times relative to immobilization for assay of particular serum biochemicals and steroid hormones during investigations of the physiology of the collared peccary.