The crystallographic direction of growth in directionally solidified magnesium alloy AZ91 has been studied by TEM and EBSP techniques in SEM. The main direction of growth is found to be $$\left\langle {11\bar 20} \right\rangle $$ . The dendrites have sixfold symmetry around the main direction, with secondary arms lying along the traces of the (0001), $$\left( {1\bar 101} \right)$$ , and $$\left( {\bar 1101} \right)$$ -planes, respectively. The secondary arms lying in the basal plane are crystallographically of the same type as the main direction: $$\left\langle {\bar 12\bar 10} \right\rangle $$ and $$\left\langle {2\bar 1\bar 10} \right\rangle $$ .