Simultaneously interpenetrating polymer networks were prepared from polyrmethyl aery-late- 2- (dimethylamino)ethyl methacrylate]/epoxy resin [P(MA-DMA )/EP]. Mechanical properties of IPNs were measured. A single glass transition teinperature and a better compatibility were observed. This shows that the sample is the mixed polymer of cross-linking and interpenetrating networks. When P(MA-DMA)/EP= 20/80, there exists positive synergistic. effect. (Tg)calcd was calculated by Fox equation and it was found that ...