Three new antimicrobial bisbenzylisoquinoline alkaloids, thalmirabine (3), thalistine (11), and O-methylthalibrine (18) were isolated from the roots of T. minus L. Race B and characterized by spectral and chemical methods. Additional alkaloids, not previously reported from this source, are S-methylcorydaldine (1), thalrugosine (2), thalphenine (22), columbamine (23), thalifendine (24) and jatrorrhizine (25). To date, sixteen alkaloids have been reported from the roots of Thalictrum minus L. race B (Ranunculaceae) (1, 2, 3), some of which possess hypotensive and antimicrobial properties. In this paper we present the isolation and identification from this source of nine additional alkaloids, of which three are new natural products. Five were obtained from the ether-soluble tertiary nonphenolic fraction, the so-called Fraction F of an earlier publication (2); while four were quaternary alkaloids derived from Fraction E. The compounds are presented in the order of elution from the first chromatographic column.