The newdimeric alkaloid arundaphine, a tryptamine-tryptamine base, was isolated from roots and rhizomes of Arundo donax (Poaceae). Spectral data and an x-ray structure analysis established its structure as 1-[3-(2- dimethylaminoethyl)-5-hydroxy-1H-4-indolyl]-3-hydroxy-3-(2-methylaminoethyl) -2-indolinone.