Abstract Transmural potential difference, short circuit current, and electrical resistance were all appreciably greater when measured from noneverted rat jejunum in vitro than from everted jejunum. Everting the small intestine apparently decreases active ion transport but increases passive permeability. During the first few minutes of incubation at 37° (following preparation at 0°), potential difference rapidly declined with both everted and noneverted orientations. This decline was caused entirely by a drop in net ion fluxes, since during this time electrical resistance either remained constant or slightly increased. Adequate interpretation of these results must await further study. In the meantime it is worth knowing that important transport properties of intestine are drastically influenced by the common experimental expedient of eversion.