'Mate' or 'Yerba mate' (Ilex paraguariensis, Aquifoliaceae) is a tonic and stimulant beverage widely used in South America. It is also traditionally used in gastrointestinal disorders as eupeptic and choleretic agent. Accordingly, the effect of decoctions of the leaves of I. paraguariensis and three of its substitutes or adulterants (Ilex brevicuspis, Ilex argentina and Ilex theezans) on bile flow (BF) and intestinal propulsion were investigated. I. paraguariensis and I. brevicuspis induced an increase in BF, while the latter also enhanced intestinal transit. In contrast, neither I. argentina nor I. theezans exerted any effect on BF or intestinal propulsion. These results suggest that the therapeutic properties of I. paraguariensis will be affected when at least an adulterant is present in the final commercial product of Yerba mate.