Castor oil, lipopolysaccharide of Escherichia coli, and endotoxin of Salmonella typhimurium were used for inducing diarrhoea in sham operated or caecectomized mice. Copious diarrhoea was induced by lipopolysaccharide (LPS) in caecectomized mice. Characteristics of diarrhoea induced by castor oil were not different between the two groups. It is concluded that caecectomized mice may be a good model to study lipopolysaccharide-induced diarrhoea.