An aqueous dispersion of a copolymer of at least one 3,4-alkylenedioxythiophene compound with a solubility in water at 25.degree. C. of less than 2.2 g/L with at least one 3,4-alkylenedioxythiophene compound with a solubility in water at 25.degree. C. of at least 2.2 g/L and a polyanion; a preparation process therefor; its use for coating; a printing ink containing the aqueous dispersion; an electro-conductive layer containing a copolymer of at least one 3,4-alkylenedioxythiophene compound with a solubility in water at 25.degree. C. of less than 2.2 g/L with at least one 3,4-alkylenedioxythiophene compound with a solubility in water at 25.degree. C. of at least 2.2 g/L and a polyanion derived from an aqueous dispersion thereof; and an antistatic layer containing a copolymer of at least one 3,4-alkylenedioxythiophene compound with a solubility in water at 25.degree. C. of less than 2.2 g/L with at least one 3,4-alkylenedioxythiophene compound with a solubility in water at 25.degree. C. of at least 2.2 g/L and a polyanion derived from an aqueous dispersion thereof.