A new bisbenzylisoquinoline alkaloid (-)-(1S, 1 ′R)-O,O′ -dimethylgrisabine (1) was isolated from the leaves of Phaeanthus vietnamensis Ban. Its structure was determined on the basis of the extensive 2-D and 1-D nmr long-range heteronuclear correlations. Its antibacterial activity is also described. © 1990.