The wood anatomy of 67 species of Erythroxylum, Nectaropetalum and Pinacopodium was analysed from an ecological, systematic and evolutionary perspective. Wood anatomy variation within the pantropical genus Erythroxylum is explicable largely in relation to ecological factors and correlative differences in plant architecture, leaf size and duration and foliar anatomy. Wood anatomy ranges between primitively mesomorphic and either meso- or xeromorphically specialised. Wood inclusion type and leaf structural features are strongly interrelated, thus reflecting both taxonomic affinities and ecological profiles of the species. The most wood anatomically variable infrageneric taxa within Erythroxylum are the New World sections Archerythroxylum and Rhabdophyllum, which include architecturally diverse, deciduous and evergreen species. Due to the intergrading ranges of wood anatomical variation among consectional and/or sympatric Erythroxylum species, attempts to identify wood samples to the species level are ill-advised in the absence of complementary ecological, geographic and leaf structural data. The wood anatomical uniformity of the cultivated cocas and their closest wild relatives of sect. Archerythroxylum implies their shared mesophytic ancestry, whereas chemical, genetic and leaf structural differences reflect the long term human selection, isolation and cultivation of Erythroxylum within ecologically disparate regions of South America. Wood (and leaf) anatomy of the drought sensitive E. coca var. coca is the most primitive and mesomorphic of the cultivated cocas, whereas both drought tolerant varieties of E. novogranatense are more wood (and leaf) anatomically specialised. The closest affinities of the Erythroxylaceae to other families of the Geraniales-Linales-Malpighiales alliance occur among the most wood anatomically primitive, mesomorphic and putatively basal, evergreen taxa within each family.