The present study consisted of twelve genotypes of flax which were evaluated over twelve environments (2 seasons (2013/14 and 2014/15), 2 locations (Etay El-Baroud Exp. Sta., El-Beheira Governorate and Ismailia Exp.Station, Ismailia Governorate) and 3 plant density (1000,1250 and 1500 seeds/m2)) These materials were evaluated in a split plot design with three replications at the twelve environments which-mentioned before. The mean square of environments (E) genotypes (G), and E x G interaction for all studied traits revealed highly significant differences, indicating a wide range of variation among genotypes, environments and these genotypes exhibited differential response to environmental conditions. The significant variance due to residual for all characters indicated that genotypes differed with respect to their stability suggesting that prediction would be difficult, which means that mean performance alone (mean yield) would not be appropriate. Interaction component of variance (σ2ge) was less than the genotypic variance (σ2g) for all characters except each of straw weight per plant, plant height and capsules number per plant. This was reflected in high value of heritability and low gap between GCV and PCV values for 1000 – seed weight, fiber percentage, oil percentage, seeds number per capsule, and technical length. These results indicating the possibility of using technical length as selection index for improving straw weight/plant and both of number of seeds per capsule and 1000- seed weight as selection indices for improving seed weight/plant. The criterion, yield stability (YSi) statistic indicated that only one genotype (S.541- D/4) exhibited superiority and stability for all straw characters, in addition to S.435-11/10/3 for each of straw yield/fad, technical length and plant height. Also, S.541- /6 gave high mean performance and stability (YSi) for seed yield/fad, oil yield/fad, 1000- seed weight and oil percentage. Therefore, the two strains (S.541-D/4 and S.435/11/10/3) may be recommended to be included in any breeding program for improving straw yield and its related traits and also, S.541-C/6 for improving seed yield and its related characters. Straw weight/plant was positive and significant correlated with each of technical length, plant height, and seed weight/plant. And also, plant height exhibited positive correlation with technical length. Whereas, seed weight per plant, exhibited positive correlation with both of capsules number/plant and 1000 - seed weight. Whereas, the correlation between oil percentage with both of 1000- seed weight and capsules number per plant was positive. These mean that the possibility of using both of technical length and plant height as selection indices for improving straw weight/plant and both of1000-seed weight and capsules number/plant and as selection indices for improving seeds weight/plant.