A new carboline alkaloid, 1-(7-methoxy-quinolinyl-4-yl)-3,4-dihydro--carboline (1), was isolated from the leaves and twigs of Trigonostemon lii Y.T. Chang, together with three known ones, trigonostemonines C and D (2 and 3), and trigonoliimine A (4). Their structures were elucidated by spectroscopic analyses, including 2D-NMR techniques.