In studies of rat jejunum, par-enteral bethanechol increases the transmu-ral PD, and decreases Na and HCO3 absorption, the rate of H secretion, and the final PCO2. In the ileum, it increases the final pH slightly. Bethanechol has no effect on intestinal transport when added to lumenal fluid. The changes in net transport evoked by pilo-carpine are quantitatively similar in jejunum and ileum, whereas the major effect of bethanechol is on the jejunum, implying that the muscarinic receptor of the ileum is less accessible or less responsive to bethanechol.