We have described a technique for the measurement of transmural electric potential difference in the intact human intestine. There was a marked enhancement of luminal negativity in the small intestine in the presence of glucose and galactose, but not in the presence of sugars which are not actively transported. Neither base line nor glucose-evoked potentials in the small intestine were measurably affected in acute cholera. The diarrhea in this disease is, therefore, produced by a mechanism which does not substantially alter the normal intestinal transmural electric potential, and the intestinal capacity for sugar-dependent sodium transport probably remains intact.