This experiment is part of a series of studies on animal welfare. It was performed in order to determine whether surgical castration of piglets induces pain in the days following the surgery using behavioural indicators. The behaviour of the piglets was registered during 5 days with cameras. Two types of behavioural methods were applied: scan sampling and continuous observations. Numerous indicators were analyzed (location, posture, displacement, suckling, play, agonistic behaviours, tail movement, spams, stiffness, scratching etc.) and compared in piglets submitted or not to surgical castration. Overall, the results confirm that castration induces pain and that pain-related responses are exacerbated during the first few hours following castration. However, many alterations persist beyond 24 h and some of them are still present 4 days after castration. This suggests that piglets suffer from pain for more than a few hours following castration.