This communication reports a new dimeric benzylisoquinoline-aporphine alkaloid, adiantifoline (IV), isolated from the nonphenolic tertiary alkaloid fraction of the roots and tops of Thalictrum minus L. var. adiantifolium Hart. Adiantifoline crystallized from absolute ethanol as pale yellow needles, m.p. 143.5-144°C, [α]D²⁸ + 90° (c 0.11, MeOH), and showed a UV spectrum almost identical to that of thalicarpine (I). Its NMR spectrum in deuterochloroform at 80 MHz exhibited two N-methyl peaks at 2.44 and 2.47 δ, eight O-methyl groups, six aromatic protons, and 14 methylene and methine protons. The mass spectrum and elemental analysis supported the formula C₄₂H₅₀N₂O₉ (mol. wt. 726). Permanganate oxidation of adiantifoline gave compound VI, and sodium-liquid ammonia cleavage yielded a phenolic fraction (superimposable with the hydroiodide salt of 6'-hydroxylaudanosine from thalicarpine) and a nonphenolic fraction (compound IX, C₁₈H₂₅O₂N). Comparison with thalicarpine, along with ORD and CD curve analysis, suggested adiantifoline has the same stereochemistry as thalicarpine and the extra methoxy group at the C-3 position. Due to insufficient amounts of adiantifoline, the stereochemistry of the two asymmetric centers and total oxygenation pattern were not fully determined, and synthetic studies for final structure proof are in progress.