Berbidine 111, the first simple isoquinoline-isoquinolone dimer, has been obtained from Berberis brandisiana of Pakistani origin. The botanical family Berberidaceae is known for the production of isoquinoline alkaloids, including in particular bisbenzylisoquinolines (1). Presently, as a result of an investigation of the alkaloids of Berberis brandisiana Ahrendt, a plant native to the mountains of northern Pakistan, we report the isolation and structure elucidation of berbidine {l}, C23H28N205, u max (CHCI,) 1605, 1640 cm-', which is the first known simple isoquinoline-isoquinolone dimer. We believe that this alkaloid throws new light upon the catabolism of bisbenzylisoquinolines.