Copolymerization of 4-vinylpyridine (4VP) with styrene (St) was performed in ethanol using 2,2’-azobisisobutyronitrile (AIBN) as an initiator, and then a random copolymer P(4VP-St) was obtained. A soluble pyridinium-type polymer containing N-benzyl-4-vinylpyridinium bromide [Q-P(4VP-St)], was prepared by quaternization of P(4VP-St) with benzyl bromide (BzBr). The structures of P(4VP-St) and its quaternized product Q-P(4VP-St) were identified by FTIR. The 4VP content in P(4VP-St) and the pyridinium group content (C-q) in Q-P(4VP-St) were determined by nonaqueous titration and argentometry, respectively. The molecular weight of p(4VP-St) was characterized by intrinsic viscosity. In addition, the charge density sigma of the soluble pyridinium-type polymers was measured by colloid titration, and the mathematical relation between sigma and C-q was established as follows : sigma = -0.090 + 0.942 C-q. A preliminary investigation was made into the viscosity behavior and electroconductivity of the Q-P(4VP-St)/polar solvent system.