Eighty-three calves with a complicated umbilical hernia were included in a randomised prospective study. The frequency of wound infection was compared in two groups. The first group received antibiotics for one day, the second group for four days. The infection rate in calves receiving antibiotics for one day was 25 per cent compared with 8 per cent in calves treated for four days (P less than 0.05). Male calves were more susceptible to infection than female calves.