This genetic variation of Acacia crassicarpa was studied on 8-10 year old progeny tests located at Carn Lo - Quang Tri and Phong Dien - Thua Thien - Hue. The aim of the studies reported here was to obtain knowledge of genetic factors associated with growth, stem straightness and their genotype by environment interaction with growth and stem straightness in order to facilitate improvement of A crassicarpa for pulp production. The results showed that there were significant differences on growth traits and stem straightnes between families within provenances in 10 year old trial at Cam Lo and 8 year old trial at Phong Dien. The 5 best families exhibited significantly greater stem volume (exceeded from 40 to 106 percent) than the volume of the 5 worst families and average volume of the trials. MAI of 5 elite families ranged from 25 to 28 m3/ha/year at Carn Lo and from 19 to 24 m3/ha/year at Phong Dien. This farniliy selection could result in faster improvement of productivity and stem quality by deployment of the best families. Narrow-sense heristablities of growth traits and stem straightness in both progeny tests were medium values (ranged from 0.2 to 0.4), but coefficent of additive variations (CVa) were high (CVa 5 percent). Therefore, the findings clearly demonstrate that there is high potential to improve tree growth and stem straightness in Quang Tri and Thua Thien - Hue. Optimun age for breeding of A crassicarpa could be at age of 5 years in bare-hill soil areas or age of 8 years in areas of interior-sandy soil. G x E effects are practically important for growth and stem straigthness that different family should be used on different sites. Therefore, different breeding population of A crassicarpa should be set up in these sites.