The anatomy of leaf, node, twig, and bark of Ilex, Nemopanthus, Oncotheca, Phelline, and Sphenostemon is described, together with the wood anatomy of the 4 latter genera. Several characters are recorded for the first time. The systematic value of some anatomical characters for judging the wider affinities of the genera involved is discussed. Considering these characters together with macromorphological and palynological data, it is concluded that Phelline and Sphenostemon each merit family status, and have affinities with Aquifoliaceae and Icacinaceae of the Celastrales. Oncotheca shows no affinities with the families of Celastrales, and may possibly have its closest relatives in Theales, but this problem has not been studied in great detail. The leaf anatomy of 95 Ilex species is described, and the great leaf anatomical diversity of Ilex is discussed with reference to Loesener’s infrageneric classification. In general, leaf anatomy cannot be used to support his elaborate subdivision of the genus. Infraspecific leaf anatomical variability is reported and discussed for 15 species of Ilex. Attention is paid to some geographical, ecological, and functional aspects of the leaf anatomical range of variation in Ilex. This range has a general significance for systematic leaf anatomy, because it shows the restricted value of several characters for the discussion of affinities above the genus level.