Oxidative chemical polymerization of aniline in hydrochloric acid solution at sub-zero temperatures leads to polyaniline with a molecular weight five to ten times higher than that prepared at room temperature. The optimum polymerization temperature to give a polymer with the highest yield and molecular weight has been determined, and solution state C-13 n.m.r. spectroscopy shows that the improved polyaniline has fewer defect sites compared to the standard polymer. Despite these intrinsic improvements, the conductivity is of the same order of magnitude as standard polyaniline. A solvent-cast film of polyaniline camphorsulfonate had a conductivity of 295 S cm(-1), although this rose to 820 S cm(-1) along the stretch direction after the film had been uniaxially oriented. An oriented film cast from N-methyl-2-pyrrolidone solution and protonated with methanesulfonic acid showed a conductivity of 260 S cm(-1) along the stretch direction and 31 S cm(-1) perpendicular to this.