The aim of this study was to evaluate the effect of genetic materials and the radial variability on anatomical structure and basic density of wood from Eucalyptus spp. and Corymbia citriodora and also to verify the influence of the anatomy on the wood basic density. Two natural hybrids of Eucalyptus urophylla and Corymbia citriodora species were studied, wherein three trees per genetic material were sampled in the state of Minas Gerais, Brazil. Nine discs (one in each tree) were removed at 1.30m from the ground and from these we obtained properly oriented specimens in the pith to bark direction, for determining the anatomy and wood density among the genetic materials and radial positions. Compared to the hybrids, C. citriodora showed higher values for thickness, wall fraction and wall portion of the fibres and also basic density. The species also showed less pronounced radial variation of the anatomical structure, demonstrating greater uniformity of wood in the pith-bark direction, important characteristics for lumber purposes and drying, among other applications that require a more homogeneous raw material. The wall fraction and the wall portion of the fibres were the anatomical parameters that better explained the radial variation of basic density.