Two series of Eucalyptus dunnii field trials were established at two locations in the north of Guangxi province in south central China between 1988 and 1991 to examine growth performance and genetic variation of trees from I 0 natural seed sources. After four years, mean heights in the trials ranged up to 14.2 m and mean diameters at breast height up to 12.0 em. Significant differences between seed sources existed for height and diameter and there were significant seed source by environment interactions in height and diameter across sites. However absolute magnitudes of differences between seed sources were small and changes in performance across sites were relatively unimportant. No one seed source showed absolute superiority at both locations across assessment ages. Seed source within the natural range is concluded to be of minor importance for optimising growth in plantations of the species though the variation within seed sources may be important for future domestication and tree improvement.