Microwave heating of different polymer systems (epoxy-amine. polypropylene-iron, carbon-black-filled perfiuoroelastomer) was evaluated using dielectric testing and monitored processing in a multimode microwave cavity. Dielectric measurements were made using a field perturbation technique and a transmission/reflection technique. The electric loss factor of the epoxy system continuously decreased during cure. Results for the microwave heating of the polypropylene-iron composites show that heating is enhanced with increased iron concentration and smaller iron particle size, although the penetration depth of the microwaves Is decreased, especially after the onset of percolation. A novel solidstate processing technique for thermoset systems was also evaluated. By milling the reactants to a fine powder, and mixing them completely, the extent to which diffusion limited the process was significantly reduced: increased milling resulted in higher activation energies. In addition to the inherent advantages of solid-state processing. it Is possible that processing times for solid-state processing could approach processing times for traditional melt processing.