This paper studies the relationship between apparent density and some anatomical properties of Eucalyptus nitens such as vessel frequency, vessel area, ring width, fiber cell wall thicknesses, and fiber length. The study involved 29 trees from 10 families of Eucalyptus nitens cut from a 17-yr-old plantation in Southern Chile. The properties were determined along the radial direction of the trees by using X-ray equipment and at selected positions through microscope and fiber quality analyzer equipment. The results showed that the anatomical properties of E. nitens did not change gradually from pith to bark, but they were better described by dividing the tree radius into three different wood-zones referred as inner-, middle-, and outer-wood. The apparent density of E. nitens was dependent of the vessel area, cell wall area, ring width, and latewood width. The correlation coefficient between apparent density and vessels area was negative and the correlation coefficient between apparent density and cell wall area, latewood ring width, and total ring width were positive. These means that E. nitens wood with lower density tended to have higher vessel area, and lower fiber cell wall area, ring width, and latewood width.