In several species the epidermal growth factor (EGF) is known to be a potent mitogen which ensures the integrity of the gut mucosa. In the pig its role in the gut was not investigated. Antisera against recombinant porcine EGF were raised in rabbits. The antiserum was used to screen EGF-immunoreactivity in histological sections of the duodenum and jejunum of healthy piglets and piglets with diarrhoea. The specificity of the staining reaction was ensured. Immunoreactivity was found in all goblet cells and their mucus but not in other cells of the gastrointestinal tract. The number of goblet cells in the duodenum of the sick animals was nearly twofold compared to healthy piglets. In the jejunum, the number of goblet cells was less strikingly increased in the piglets with diarrhoea (20%), but the mucus granule size was 2-fold. These data support the assumption that EGF from the goblet cells serves as a surveillance factor for gut mucosa integrity in the pig.