Plants of the Amaryllidaceae family, including ca. 60 genera and about 800 species, are among the top 20 in the most widely applied medicinal plant families. Numerous pharmacologically active compounds, such as phenols, alkaloids, lectins, peptides, etc., have been identified and characterized from this family. As primary constituents, more than 700 structurally diverse Amaryllidaceae alkaloids have been isolated to date. These biogenetically related alkaloids are basically classified into 25 different skeleton types according to their ring systems. Representative structures for each type of Amaryllidaceae alkaloids are shown in this chapter. Biosynthetic pathways for each type of Amaryllidaceae alkaloids including those newly established subgroups are also discussed. In addition, recent reports on the occurrence and biological activity profiles of Amaryllidaceae alkaloids are summarized.