Thirty-eight lambs with watery mouth were presented alive for necropsy. The most frequently found abnormality was enteritis, in 25 lambs. Bacteria were cultured from the gut contents of all lambs and bacteraemia was detected at high frequency at necropsy, though very much less frequently six hours before. Escherichia coli strains did not possess K99 antigen. It was concluded that absolute starvation and septicaemia were unlikely causes of the disease; that there is support for the hypothesis that reduced gut motility is an important early feature and, that if bacteria are involved in the aetiology, they may have a non-specific role.