Cortisol, acute-phase protein concentrations, immune function, feed intake, growth, and behavior were measured in order to determine the effect of repeated ketoprofen (K) administration to surgically castrated bulls. Treatments consisted of control (C), surgical castration at 0 minutes (S), surgical castration 20 minutes after an i.v. injection of 3 mg/kg of BW of K (SK1), surgical castration at 0 and 20 minutes after an i.v. injection of 1.5 mg/kg of BW of K (SK2), or surgical castration following 1.5 mg/kg BW i.v. injection of K at 20 minutes and 0 minutes and 3 mg/kg of BW injection of K at 24 hours (SK3). Castration increased plasma cortisol concentrations in S and K treated animals compared with C, but there were no differences in peak and interval to peak cortisol responses among the groups. Overall, cortisol response was highest among castrates. K treatments decreased this response compared to S alone. Plasma haptoglobin and fibrinogen concentrations were increased on day 3 in the castration groups compared with C. Alternatively, SK1 and SK2 had lower haptoglobin concentrations than S animals. Concanavalin A-induced interferon-ã production was suppressed in S and SK3 groups compared with C, SK1, and SK2 groups. Overall, from day 1 to 33, dry matter intake was lower in S, SK1, and SK3 groups than in C animals. During days 1 to 35, ADG was lower for S, SK2, and SK3 groups compared with C animals. Standing posture was more frequent than lying in the S group compared with C during the first 6 hours after treatment. This higher incidence of abnormal standing postures seen in S was reversed by the K treatments. Conclusions stated that plasma cortisol and acute-phase proteins were increased by surgical castration while immune function, feed intake and ADG were decreased. Administration of ketoprofen effectively decreased the cortisol response to castration, although there were no advantages in treating with 2 split doses of K. Repeating the K dose 24 hours after castration had no influence on changes in acute-phase proteins and immune response. Analgesia with K was an effective method for alleviating acute inflammatory stress associated with surgical castration.