Ion transport was measured in jejunal biopsies using short-circuit current (SCC) as an index of net electrogenic ion transport. Increases in SCC associated with stimulation of Cl- secretion were observed in control tissues, but CF tissues did not exhibit such a response, indicating a failure of intestinal Cl- secretion. The rise in SCC associated with Na(+)-linked glucose absorption was greater in CF tissues than in controls, reflecting an enhanced active absorption of glucose.