Heartwood content was studied in 27 Eucalyptus globulus Labill. trees with spacings 3 x 3, 3 x 2, and 2 x 1 (m x m), with 9 years, from a 1st rotation spacing trial. The height attained by heartwood increased with total tree height independently of spacing, and reached on average 45%, 59%, and 62% of total height, respectively, for spacings 2 x 1, 3 x 2, and 3 x 3. In all the spacings, the heartwood radius decreased gradually along tree height, and the radial thickness of sapwood remained practically constant at approximately 16 mm in the lower part of the stem (