(Ti,Zr)B-2-(Zr,Ti)C ceramics were synthesized by reactive hot-pressing and solid solution coupling effect using ZrB(2)and TiC powders as starting materials. Effects of sintering temperature on phase relations, microstructure and mechanical properties were reported. The equimolar ZrB(2)and TiC reactants ensured a complete in situ reaction to form (Ti,Zr)B(2)and (Zr,Ti)C solid solutions. The (Ti,Zr)B-2-(Zr,Ti)C composite sintered at 1750 degrees C was fully densified, and exhibited a high hardness of 29.1 GPa due to fine-grain hardening and solid solution hardening. The optimized comprehensive mechanical properties such as a hardness of 27.9 GPa, a strength of 705 MPa and an indentation fracture toughness of 5.3 MPa m(1/2)were achieved in (Ti,Zr)B-2-(Zr,Ti)C composites sintered at 1800 degrees C for 1 hour.