Changes in the plasma concentrations of cortisol were recorded in 5–6 weeks-old lambs during the first 480 minutes after surgical castration and tailing in order to define the full post-treatment cortisol response and to determine whether or not the handling associated with repeated blood sampling delayed the return of cortisol concentrations to pretreatment values. Four groups of six or seven lambs were studied: One group was bled regularly throughout the 480 minutes of the study, and in the other three post-treatment blood sampling began at 90, 240 or 480 minutes. Plasma cortisol concentrations increased after treatment and returned to or approached pretreatment values by 480 minutes. No significant differences in mean cortisol concentrations were observed between the groups at any stage. It is concluded that the acute distress response of these lambs to surgical castration and tailing lasted about 8 hours and that repeated handling for blood sampling did not contribute significantly to this distress.