The effects of acute oral administration of erythrinian alkaloids, i.e. (؉)-a a-hydroxy-erysotrine, erythravine and (؉)-11a a-hydroxy-erythravine isolated from the flowers of Erythrina mulungu were investigated in two animal models of anxiety in mice-the light-dark transition model (LDTM) and the elevated plus-maze (EPM). In the LDTM, erythravine (3, 10 mg/kg) and (؉)-11a a-hydroxy-erythravine (10 mg/kg) increased the time spent by the animals in the illuminated compartment and (؉)-11a a-hydroxy-erythravine (3 mg/kg) increased the number of transitions between compartments of the LDTM, suggesting an anxiolytic-like effect of these erythrinian alkaloids. Nevertheless, the third alkaloid studied, (؉)-a a-hydroxy-erysotrine, did not change any behavioral response with the range of doses used (3-10 mg/kg). Since the oral administration of the crude extract of E. mulungu (EM) (100-400 mg/kg) did not modify the conventional measures of anxiety in the EPM, this animal model was not chosen to evaluate the anxiolytic properties of the isolated alkaloids. These results suggest that the alkaloids erythravine and (؉)-11a a-hydroxy-erythravine are responsible for the anxiolytic effects of the crude extract of E. mulungu.