In order to get an insight of the relations between the compositions, the microstructures and the mechanical properties, the experimental high-temperature structural intermetallic alloys comprised of L2_1-type(Co,Ni)_2AlTi and L1_2-type(Co,Ni)_3(Al,Ti) ordered phases in the system Co-Ni-Al-Ti were examined for various heat-treated microstructures by compression testing and fracture analysis. Some approaches to further improving the high-temperature strength and room-temperature ductility are discussed.