The precipitation polymerization of aniline in the presence of organic acids, including toluene-4-sulfonic acid, phenylphosphonic acid, 4-aminophenylphosphonic acid, and acetophosphonic acid, led in one step to conductive polyaniline. The polyaniline showed very good affinity for water and was easily modified to be water-soluble. In comparison with the widely studied postpolymerization. of doped polyaniline, this reaction allowed reasonably good conductivity to be achieved at a lower acid/polyaniline ratio. Moreover, the easy in situ incorporation of the dopant into the polymer structure caused high stability of the created salt; that is, no dedoping was observed after it was washed with water, methanol, or other solvents.