Chromatography of an ethanolic extract of Pycnostemma manillensis over silica gel afforded phaeanthine-2'β-N-oxide (1) and pycmanilline (2) which were characterized as new bisbenzylisoquinoline alkaloids by a consideration of physicochemical data and the utilization of simple chemical reactions. Phaeanthine-2'β-N-oxide was reduced to phaeanthine while pycmanilline, a secobisbenzylisoquinoline alkaloid, was prepared via oxidation of phaeanthine.Pycnostemma manillensis Vidal (Menispermceae) is a medicinal plant indigenous to the Philippines. Decoctions of the roots of this plant have been used in the therapy of stomachache and other gastric disturbances. The genus Pycnostemma is a rich source of bisbenzylisoquinoline alkaloids, with sixteen different compounds of this type having been isolated from among five different species. There have been, however, only two reports concerning the alkaloids of P. manillensis. In 1935, the presence of an incompletely characterized alkaloid designated ambalinine (C18H21O3N, mp 203-204°C) was reported. Some twenty five years later the second report appeared and detailed the isolation of the bisbenzylisoquinoline alkaloids berbamine, pycnamine, isotetrandrine and phaeanthine from the roots of this species. This paper is to report the isolation and identification of two new benzylisoquinoline-derived dimeric alkaloids, phaeanthine-2'β-N-oxide (1) and pycmanilline (2), as well as the reisolation of phaeanthine (3), isotetrandrine (4), pycnamine (5) and berbamine (6).