Auranofin, applied either mucosally or serosally, increased the potential difference and short-circuit current generated by stripped sheets of rat mid-intestine in a concentration-dependent manner. In-vivo auranofin induced a net fluid secretion, suggesting that the rise in electrical activity represented a stimulation of anion secretion. Removal of chloride or addition of frusemide inhibited the auranofin-induced increase in short-circuit current, indicating that chloride was the anion involved and in the case of serosal auranofin this was confirmed by direct measurement of ion fluxes. The effects of both mucosal and serosal auranofin were calcium-dependent. The gold component of the auranofin molecule is probably responsible for its secretory actions as these were mimicked by chlorauric acid. The ability of auranofin to stimulate intestinal secretion may contribute to its diarrhoeagenic action.