An investigation of the microstructural evolution and dissolution phenomena in a Ti(C0.7N0.3)-xWC-yNbC-20Ni system is reported. In Ti(C0.7N0.3)-yNbC-20Ni systems, a phase separation occurs between the TL(CN) core and the (Ti,Nb)(CN) rim phases when the system contains >15 wt% NbC, This phase separation results from the increased misfit between the cores and the solid-solution rim phases with the addition of NbC, Based on data obtained from a previous study and compositional analyses of the rim structure of the Ti(C0.7N0.3)-yNbC-20Ni system, the average dissolution rates of WC and NbC appear to be approximately the same with respect to that of TI(CN), under given sintering conditions (1510 degreesC for 1 h), In addition, compositional changes in the rim structure of the Ti(C0.7N0.3)-xWC-yNbC-20Ni system are compared with those for a Ti(C0.7N0.3)-xWC-20Ni system to explain the effect of NbC on WC dissolution in the Ti(C0.7N0.3)-WC-NbC-Ni system. The presence of NbC in the Ti(C0.7N0.3)xWC-20Ni system is found to suppress the dissolution of WC.