1-Acetyl-4-methoxy-β-carboline (I), canthin-6-one (VIIIa), 1-methoxycanthin-6-one (VIIIb), and canthin-6-one-3N-oxide (IXa), and three new alkaloids, 1-(2'-hydroxyethyl)-4-methoxy-β-carboline (IIa), 1-(1', 2'-dihydroxyethyl)-4-methoxy-β-carboline (IIIa), and 1-methoxycanthin-6-one-3N-oxide (IXb), were isolated from the root bark of Ailanthus altissima SWINGLE (Simaroubaceae). The structures of IIa, IIIa, and IXb were elucidated by spectroscopic and chemical studies.