Abstract.Frog stomach transepithelial potential difference (Vt) and resistance (Rt), as well as the voltage divider ratio (VDR) and serosal membrane potential (Vs) of surface epithelial (SEC) and oxyntic (OC) cells were recorded at rest and during stimulation with histamine. Serosal membrane K+permeability was tested by sudden elevation of serosal K+concentration from 4 to 13 mmol l−1. Stimulation decreased bothVtandRtand increasedVDRof theOC(from 9.4 ± SD 3.0 to 14.4 ± 4.1,n= 10,P<0.001), whileVsremained virtually unchanged (‐66.3 ± 4.5 mV,n= 10); inSEC, however,VDRas well asVsincreased, the latter from −67.3 ± 5.9 to – 75.7 ± 7.3 mV,n= 9, P<0.001. Elevation of serosal K+reversibly diminishedVtandVSin both cell types. The transepithelial response to K+increased after stimulation. However, the cell potential response ΔVsKincreased only in the SEC (from +16.0 ± 2.9 to + 18.5 ± 2.6 mV,n= 9,P<0.001) but not significantly in theOC. We conclude that in frog stomach bothOCandSECare stimulated by histamine: theSECrespond with a hyperpolarization, which reflects an increase in their basolateral K+conductance: theOCdo not respond with a hyperpolarization, possibly because histamine increases the basolateral membrane K+conductance as well as other ion conductances which have not yet