Blood was collected at 0, 3, 6, 12, 24, 36 and 48 h postcastration and then daily for a further 6 d to determine the degree of stress following surgical or chemical castration (Chem-cast; α-hydroxypropionic acid) of Holstein calves. Stress indicators (plasma cortisol, packed cell volume, glucose, proteins, free fatty acids, creatinine, urea nitrogen and rectal temperature) were measured for all castrates and compared with entire bull calves. There were no effects on stress indicators except plasma cortisol. Plasma cortisol concentrations were significantly elevated at 3 and 6 h postcastration in castrated compared with in-tact cattle (P < 0.05). At these times, plasma cortisol concentrations in surgical castrates were greater than chemical castrates (P < 0.05). Greatest concentrations of cortisol were measured at 6 h following surgical castration (23.2 ± 0.64 μg L−1) and at 3 h following chemical castration (16.8 ± 0.49 μg L−1). Mean cortisol concentration in calves not castrated was 7.1 ± 0.26 μg L−1. From 12 h to 7 d postcastration, differences between groups for plasma cortisol were not significant. It was concluded that acute stress occurred for 6–12 h following castration and that surgical castration caused greater stress than chemical castration. There was an immediate decline in plasma testosterone levels in surgically castrated calves and these remained at undetectable levels throughout a 63-d postcastration period. Testosterone levels of chemically castrated calves declined immediately following the injection of Chem-cast but there was a gradual increase to, and long term maintenance of, low levels of testosterone which were greater than those of surgical castrates (P < 0.01) but less than those of entire males (P < 0.01). Palpation indicated severe testicular degeneration in chemically castrated males. The average daily gains (ADG) over the entire experimental period of 133 d did not differ between the entire males (1.1 ± 0.11 kg d−1) and surgical castrates (0.9 ± 0.05 kg d−1) or between the entire males and chemical castrates (1.2 ± 0.04 kg d−1) but ADG for chemical castrates was greater than that for surgical castrates (P < 0.05). Key words: Castration, Chem-cast®, stress, cattle, cortisol, testosterone