Ailanthus altissima (Mill.) Swingle, Syn. A. glandulosa Desf. (Simaroubaceae), is a large tree indigenous to China. It is known as the “Tree of Heaven” and has been the subject of several chemical studies. The presence of quassinoid-type bitter principles (1-6), flavonols (7,8), and 2,6-dimethoxy-p-benzoquinone (9,10) has been reported in earlier papers. Recently, a series of four canthin-6-one substances were isolated and identified from the wood (11) and from the root bark (12) by two groups of authors working independently of each other. In this work, three alkaloids were isolated and identified from the leaves of A. altissima. © 1984, American Chemical Society. All rights reserved.