A principle factor analysis was applied to data for ten morpho physiological traits measured on five cultivars of flax grown in the Research and Experimental Station of Agriculture at Moshtohor. Zagazig University in 1990/91 and 1991/92 seasons. Three principle factors were extracted from the correlation matrix of the traits. The analysis indicted that the factor concerned with seed characters and both straw and seed yield/plant was the most important factor. Plant height and its related characters ranked second. The third factor included two traits, number of basal branches/plant and number of fruiting branches/plant. Characters that determined the nature of the source were all included in factors 2 and 3. Characters that determine the nature of “sink” were devided among the three factors. The components of yield formed factor 1. The findings of this investigation may help both biologists and flax breeders in determining traits that could be selected in order to increase seed yield of flax.