In Brazil, as in many other countries significant advances have been verified in intensive clonal silviculture with remarkable differences on parameters of growth and development between species clones and hybrids of Eucalyptus. At the same time, during recent years the concept of multiple uses of tree logs to increase the yield of the forest enterprise as cellulose and paper and solid wood has been introduced. The present paper studies the wood uniformity index and radial variability of density using x-rays densitometry of 8 year clones Eucalyptus grandis and E. grandis x urophylla in order to optimize their use. This experiment was performent at Suzano Cellulose and Paper Company Clone Plantation in San Miguel de Arcanjo-SP-Brazil. The best five clones of the species and hybrid by their silviculture characteristics were selected. Three models of radial density variation were found and the formation of three different types of wood were characterized (youthful, of transition and adult); the average value of wood apparent density in clones was 0.46 and 0.54 g/cm3 for Eucalyptus grandis and E. grandis x urophylla, respectively.