Five indole-3-alkylamine bases, viz., N,N-dimethyltryptamine, 5-methoxy-N-methyltryptamine, bufotenine, dehydrobufotenine, and bufotenidine, were isolated from the rhizomes of Arundo donax L. This is the first reported occurrence of bufotenidine and dehydrobufotenine in a plant species. A defatted ethanolic extract of the rhizomes produced hypotensive and antispasmodic effects against histamine-, serotonin-, and acetylcholineinduced spasms. Bufotenidine showed three main pharmacological actions, viz., antiacetylcholine effect which appears to lie more specific against skeletal muscle than against muscarinic sites, histamine release, and uterine stimulant. None of these actions of this compound had been reported previously.