"The Bisbenzylisoquinoline Alkaloids, reviewed in Vols. 7, 9, 13, and 16 of this treatise, represent the largest group among the isoquinoline alkaloids. Bisbenzylisoquinoline alkaloids tubocurarine, thalicarpine, tetrandrine, and cepharanthine also have interesting pharmacological properties, and for these reasons this group of alkaloids is again updated, covering in the Appendix the pertinent literature until 1985. Indole alkaloids of the rare genus Pauridiantha are presented here for the first time under the title "The Alkaloids from Pauridiantha"; these alkaloids are found almost exclusively in Madagascar, where plant extracts are used by the natives for medicinal purposes. "The Amaryllidaceae Alkaloids," reviewed in Vols. 6, 11, and 15 of this treatise, have been updated, and several new alkaloids of this class are listed. Occurrence, spectral properties, structure, synthesis, and biosynthesis of these alkaloids are covered in these chapters, and pharmacological properties whenever known are reported.