GABAergic involvement in the regulation of intestinal ion transport is suggested by the reduction in the short-circuit current generated by sheets of rat small intestine by the GABA antagonist bicuculline, although GABA itself caused no change. Bicuculline action was abolished by the inhibitor of Cl- secretion frusemide, suggesting that it involved a change in endogenous Cl- secretory tone. The effect of bicuculline appeared to be specific as it did not affect the electrical responses to glucose or exogenous secretagogues. The action of bicuculline was not observed in stripped intestinal sheets where the myenteric plexus is absent, and it was reduced by tetrodotoxin and atropine. It is suggested that endogenous GABA could be involved in the maintenance of a secretory tone in rat small intestine by acting on cholinergic mechanisms within the myenteric plexus.