This study investigates the relationship between dietary fat and ion transport in rat intestine. Animals were fed isocaloric diets with high fat content as corn oil, evening primrose oil (Efamol), fish oil, Efamol/ fish oil, olive oil, coconut oil, and butter. A low-fat (corn oil) diet was used in a control group. Biopsies of the small intestine from these animals were mounted in an Ussing chamber, and the intestinal mucosal to serosal ion transport was measured as short-circuit current (SCC). The SCC was stimulated in rats fed on diets high in polyunsaturated fatty acids such as corn oil, Efamol, fish oil, and Efamol/fish oil. SCC was also stimulated in rats fed on diets high in monosaturated fatty acids such as olive oil. Animals fed on diets high in saturated fatty acids such as coconut oil and butter, on the other hand, showed an inhibition in the SCC. To determine whether the effect of membrane lipids was mediated by a differential effect on membrane receptor proteins, the response to secretogogue challenge was studied. Biochemical agents and secretogogues including acetylcholine, noradrenaline, dibutyryl-cAMP, calcium ionophore A2318, and prostaglandin E2 were analysed and compared. These agents were able to influence the SCC, showing responses with marked differences between diet groups.