Radical polymerization of acrylonitrile (AN), methyl methacrylate (MMA) and styrene (S) has been studied under magnetic field (MF) using an AIBN initiator. The effect of MF is observed on the polymerization of AN and not on MMA and styrene. This may be due to the heterogeneous polymerization of AN (occlusion theory). The MF increases the rate of AN polymerization and polymer (PAN) yield. The overall activation energy is not influenced by the MF; however, the MF helps to reduce :he activation entropy of polymerization. The influence of MF alters the structure and properties of the polyacrylonitrile (PAN). The molecular weight (MW) of PAN prepared under MF is higher and the molecular weight distribution (MWD) is narrower than those obtained without MF. The syndiotactic stereoregularity and crystallinity of such PAN polymer is higher than that obtained without application of MF. Magnetic field enhances the thermostability and the dielectric property of PAN.