Two types of blends containing polyamide 6 and poly(propylene oxide) (PPO) were prepared. One of them was mixed with polycarbonate (PC) in a Brabender mixer. The other one was prepared in solution with the block copolymer as the interfacial agent. The blends were analyzed by C-13 nuclear magnetic resonance techniques at solid state, such as : magic angle spinning (MAS); cross-polarization MAS, and variable contact time experiment. It was observed that the addition of PC in the nylon 6/PPO system causes a hardening of it, which can be attributed to strong links, like a hydrogen bond. The ideal quantity of block copolymer added to a blend to improve the compatibility is between 5 and 10%. An increase of the quantity of this agent probably makes it act as a third component. Therefore, both PC and block copolymer can be used as an interfacial agent for nylon 6/PPO blends in an ideal composition.