Silicon nitride ceramics with 0-5 wt % silicon nitride whiskers were prepared by tape casting and gas pressure sintering at 2148 K for 4 hours. The whiskers worked as seed crystals and grew into the large elongated grains. The whiskers were aligned during tape casting. Orientations of the large elongated grains in sintered samples were controlled by stacking sequence of sheets cut from the tape. Samples of each composition had three structures; unidirectional, cross-plied, and 45 degrees rotated. Samples with the uni-directionally oriented grains exhibited anisotropy that became stronger as the whisker content increased, while samples of the other two structures did not show the anisotropy.