Abstract: Dominant height data was collected from Eucalyptus urophylla plantations growing under 7 density treatments. The variable factor dominant height was used to improve the parabolic type density effect model. The elastic analysis showed an increase of 0.452 0 % in average individual volume following 1 % decrease in density. Based on the marginal product analysis, the average individual tree volume decreased by 0.000 032 m3 following the addition of one tree per 006 hm2 and decreased by 0.001 006 m3 with 1.0 m increase in dominant height. The optimal density for different sites was calculated based on the modified density effect model (with height variable in it). When the stands were at their reference age (at the age of 6), the optimum density for E.urophylla plantation was 1 237, 1 492, 1 779, 2 100, 2 458, 2 853 trees per hectare under the site indexes 15, 16, 17, 18, 19 and 20, respectively.