Longitudinal electric resistivities of magnetized and unmagnetized plasmas are discussed based on appropriate kinetic equations. It is found that (1) for an isotropic plasma the resistivity calculated based on the kinetic equation including magnetization is about 1.5 time greater than that obtained in the theory without including magnetization, and (2) for an anisotropic plasma, the magnetized resisitivity is proportional to Te⊥Te‖-5/2 whereas the unmagnetized resistivity is proportional to Te⊥-1Te‖-1/2. The discrepancy is mainly due to the effect of the ambient magnetic field on the electron trajectory. It is also argued that the effect of dynamic shielding can be neglected in comparison with static shielding. A qualitative explanataion is given.