The striations parallel to the casting direction are the characteristic defects occurring during the unidirectional solidification of nonferrous metals such as pure Al and Sn. It has been known that the defects affect the recrystallization temperature as well as the mechanical and electrical properties of Al. However, it has not been still known about the effect of casting factors such as the casting speed, rod diameter of cast metals, and alloying elements on the occurrence of striations. In the present study, these casting factors affecting the occurrence of striation were investigated by adopting the quantitative examination of striations. Also, the relation between striation defects and feathery grain, which are very similar to the striation defects, was studied.