The aqueous ethanolic extract from the roots of Stellaria dichotoma showed an antiallergic effect on ear passive cutaneous anaphylaxis (PCA) reaction in mice (in vivo) and inhibitory activity on the release of beta-hexosaminidase in RBL-2H3 cells (in vitro). From the aqueous ethanolic extract, new beta-carboline-type alkaloids, dichotomines A (1), B (2), C (3), and D (4) and dichotomides I (5) and II (6), were isolated. The structures of the new constituents (1-6) were determined on the basis of chemical and physicochemical evidence, including the application of the modified Mosher's method. The effects of the isolated constituents on the release of beta-hexosaminidase in RBL-2H3 cells were examined, and 3 was found to show inhibitory activity (IC(50) = 62 microM). Moreover, 3 also inhibited the releases of antigen-IgE-mediated TNF-alpha and IL-4 (19 and 15 microM, respectively) in RBL-2H3 cells, both of which participate in the late phase of type I allergic reactions.