In order to successfully utilize beneficial points of strong anisotropy in the mechanical properties of the TiAl/Ti3Al lamellar structure characteristic of TiAl-based alloys, the development of directional solidification techniques, in which the lamellar orientation can be controlled with respect to the growth direction, is badly needed. However, aligning the lamellar structure is not an easy task because the alpha phase that determines the lamellar orientation is formed through the L+beta®alpha peritectic reaction for the alloy composition range of industrial interest. However, we have recently succeeded in aligning the lamellar structure of these TiAl-based alloys parallel to the growth direction by using an appropriately oriented seed from the TiAl-Si system (Ti-43at.%Al-3at.%Si). This can be accomplished even the primary solidification phase is beta through the continuous steady-state growth of the alpha phase when the alloy composition is close to but a little smaller in Al content than the phase boundary between the alpha and beta primary regions, as typically observed for binary alloys in the composition range of Ti-46~48at.%. The method to predict alloy compositions appropriate for aligning the lamellar structure of two-phase TiAl alloys of multi-component by directional solidification is proposed based on the assignment of eAl-equivalent' for each of the alloying elements. Mechanical properties such as tensile strength and elongation at room temperature and creep strength at 750°C were investigated for various DS ingots produced by this method. The results indicate that these DS-ingots exhibit by far a better valance of these mechanical properties than conventionally processed alloys.